Viewing angle magnification liquid crystal display unit

ABSTRACT

A viewing angle magnification liquid crystal display of this invention comprising: at least a backlight system containing a polarization element (A) obtained by disposing a retardation layer (b) between at least two layers, included in a reflection polarizer (a), and having respective selective reflection wavelength bands of polarized light superimposed on each other to conduct collimation for a diffusion light source; a liquid crystal cell transmitting collimated lights; a polarizing plate disposed on both sides of the liquid crystal cell; and a viewing angle magnifying layer disposed on the viewer side of the liquid crystal cell to diffuse transmitted light. The liquid crystal display can realize a thin type and have a wide viewing angle.

TECHNICAL FIELD

The present invention relates to a viewing angle magnification liquidcrystal display.

BACKGROUND ART

As a system for magnifying a viewing angle of a liquid crystal display,there has been known a method in which lights from backlight arecollimated, and only lights in the vicinity of the front, good incontrast and tone are extracted and diffused to thereby obtain a displaywith the same quality as in the vicinity of the front even when viewedat any angle (see, for example, publications of JP-A Nos. 10-333147 and10-25528).

In a liquid crystal display of this kind, however, a backlight techniqueto obtain collimated lights is difficult. In a system proposed in theabove patent literatures and others, for example, there have been manyproblems in practical aspects since a backlight system is thick, poor inlight utilization efficiency and high in cost.

In an ordinary TN type liquid crystal display without a viewing anglecompensating film, a region in which a high contrast can be acquired isonly on the order within ±20° of the front. In a case of an STN liquidcrystal, the region is rendered narrower. In order to extract onlylights in the vicinity of the front, good in display quality, thefollowing two methods are exemplified;

1) a method in which parallelism of backlight emitted lights areconfined within a range of the order of ±20° as a half value width andtransmitted light in the vicinity of the front is extended with adiffusion means after transmission of a liquid crystal cell to therebymagnify a viewing angle, and

2) a method in which only lights in the vicinity of the front within±20° are extracted from lights after transmission of a liquid crystaldisplay and spread with a diffusion means.

In the second method, however, a light loss is large and therefore, themethod has not been suited for use in liquid crystal display. On theother hand, in the first method, the parallelism is limited within arange of the order of ±40° if a prism light condensing sheet representedby BEF manufactured by 3M Corp. is employed in a back light. And bymeans of a shape of a backlight guide member is limited within a rangeof the order of ±40°, which is short in ability for use in a viewingangle magnification system of a liquid crystal display.

As a collimating means, there has been available a method employing ashielding louver represented by a light control film manufactured by 3MCorp. and others. In the method, however, there has been a problem inbrightness because of a large absorption loss in the course ofcollimation. That is, one of a thickness, brightness and a parallelismof obtained lights have to be sacrificed due to a requirement fromdesign, resulting in many of problems for putting it into practical use.Especially, for use in a note book personal computer or a cellularphone, it is desirable to use a collimation system restricted inincrease in thickness to 200 μm or less and preferably, 100 μm or less,and even in a case where a collimation system is built in simultaneouslytogether with a reflecting polarizer for adding a brightness enhancementeffect, it is desirable to restrict the maximum increase in thickness to500 μm or less, which is difficult being realized in the method.

On the other hand, there has been known collimation means with a mirror,a lens, a prism or a light guide member. In these methods, however, athickness and a weight increase greatly, which negates to establish aposition as a useful means in applications other than a projector or thelike.

Accordingly, in a viewing angle liquid crystal display, a necessity hasarisen that not only is collimation effected in a thin film structure,but a light source is also confined within about ±20°, which is a rangein which a good viewing angle characteristic of the liquid crystaldisplay can be attained, and that an absorption loss is further reduced.

In a collimation means using a shielding louver, a microlens array, aprism or the like, a moiré occurs between a fine structure and pixels ofthe liquid crystal display, thereby having disabled a good display to beobtained. Since light is not emitted from a binding portion in a prism,a clearance between lenses or the like, a regular darkness andbrightness in-plane pattern arises in emitted light, resulting in amoiré. In order to prevent a moiré, it is possible to insert a diffusionmeans, whereas a problem arises that a parallelism of obtainedcollimated lights is degraded, which has been a problem against puttinginto practical use.

Even in a case where interference between liquid crystal pixels and acollimating means was alleviated by changing a cycle in the regularity,a case was further observed where interference occurs with a finestructure of a collimated light diffusing means arranged on the displaysurface side of the liquid crystal display. In a case where a structurehaving regularity such as a microlens array, a microprism or the like isemployed in a collimated light diffusing means, interference occurs withthe fine structure thereof.

Therefore, in order to prevent interference of liquid crystal pixelswith the collimated light diffusing means, a necessity arises forcontrivance of a size of the fine structure of the collimated lightdiffusing means or a way of arrangement thereof. A design for preventinginterference with liquid crystal pixels, however, has been easy to causea problem to lead to second interference between members themselves thatwould otherwise cause no interference since the design is the same as ameans preventing interference of the collimating means with the liquidcrystal pixels.

For example, if a collimating means adopts a size of a structure notinterfering with the liquid crystal pixels, a collimated light diffusingmeans similarly adopts a size of a structure not interfering with theliquid crystal pixels; therefore, both means result in having the sizesinterfering with each other. This applies to a contrivance of angles andarrangement in a similar way, which has narrowed a range of an allowabledesign and restricted a selectable optical system within an extremelysmall range.

In such a way, a viewing angle magnification system consisting of acollimating means and a collimated light diffusing means has limitedoptions in design because of an optical problem caused by respectivefine structures, having lead to difficulty putting the system intopractical use.

Investigation about collimation for a light source using a specialoptical film has been conventionally conducted in addition to a typethat employs surface structures, refraction and reflection that requiresa large depth and an air interface such as a lens and a mirror prism anda front light condensation/collimation system accompanied by a largeabsorption loss such as a shielding louver.

Typical methods thereof include a method in which a bright-line lightsource and a band pass filter are combined. Exemplified are: apublication of JP-A No.6-235900 which is filed by Phillips Corp., apublication of JP-A No. 2-158289 a publication of JP-N No. 10-510671,the specification of U.S. Pat. No. 6,307,604, the specification of DENo. 3836955, the specification of DE 4222028 A1, the specification of EPNo. 578302 A, the specification of USP No. 2002/34009 A, a pamphlet ofWO 02/25687 A1

A method can be exemplified in which a band pass filter is provided on abright-line emitting light source/display unit such as CRT orelectroluminescence, which are described in the specification of JP No.2001/521643 A and the specification of JP No.2001/516066 A.

Furthermore, exemplified is a method in which a band pass filter adaptedfor three wavelengths is provided to a bright-line cold cathodefluorescent lamp that is described in the specification of USP No.2002/36735 A filed for a patent by Fuji Photo Film Co., Ltd. andpublications of JP-A Nos. 2002-90535 and 2002-258048 filed by NITTODENKO CORPORATION; or the like.

The techniques do not function unless a light source has a bright-linespectrum. Therefore, a problem has remained that is related to designand manufacture of a film selectively functioning for a specificwavelength. In addition, in a case where a band pass filter is of anevaporated interference film, even a reliability problem has existedthat a wavelength characteristic alters due to a change in refractiveindex of a thin film in a humidified environment.

On the other hand, as a collimation system employing a hologrammaterial, exemplified are the specification of U.S. Pat. No. 4,984,872filed by Rockwell Co. and others. A material of this kind is high in afront transmittance, while an obliquely incident light cannot beperfectly reflected and removed off. In a case where a directtransmittance is measured with incident collimated light, a hightransmittance is measured in the front direction because the lightpasses through as is, while a low transmittance is measured forobliquely incident light because the light is scattered, with nodifference observed between transmittances in both cases when adiffusion light source is employed. Therefore, in a case where thesystem is disposed on an actual diffusion backlight light source, alight condensing function cannot be sufficiently satisfied. Many ofhologram materials are soft and weak, having lead to many problemsrelated to reliability.

It is an object of the present invention to provide a liquid crystaldisplay of a thin type and capable of realizing a wide viewing angle.

DISCLOSURE OF THE INVENTION

The present inventors have been conducted serious studies in order tosolve the task with the result that a viewing angle magnification liquidcrystal display described below has been found, which leads tocompletion of the present invention. That is, this invention is asfollows:

1. A viewing angle magnification liquid crystal display comprising atleast:

a backlight system containing a polarization element (A) obtained bydisposing a retardation layer (b) between at least two layers, includedin a reflection polarizer (a), and having respective selectivereflection wavelength bands of polarized light superimposed on eachother to conduct collimation for a diffusion light source;

a liquid crystal cell transmitting collimated lights;

a polarizing plate disposed on both sides of the liquid crystal cell;and

a viewing angle magnifying layer disposed on the viewer side of theliquid crystal cell to diffuse transmitted light.

2. The viewing angle magnification liquid crystal display according toabove description 1, wherein

the selective reflection wavelengths of the at least two layers of thereflection polarizer (a) are superimposed on each other in thewavelength range of 550 nm±10 nm.

3. The viewing angle magnification liquid crystal display according toabove description 1 or 2, wherein

the reflection polarizer (a) is a circular polarization type reflectionpolarizer (a1) transmitting circularly polarized light but selectivelyreflecting reverse circularly polarized light, and

the retardation layer (b) comprises a layer (b1) having a frontretardation (in the normal direction) of almost zero and a retardationof λ/8 or more relative to incident light incoming at a directioninclined from the normal direction by 30° or more.

4. The viewing angle magnification liquid crystal display according toabove description 1 or 2, wherein

the reflection polarizer (a) is a linear polarization type reflectionpolarizer (a2) transmitting one of linearly polarized lightsperpendicular to each other, but selectively reflecting the otherthereof,

the retardation layer (b) comprises a layer (b1) having a frontretardation (in the normal direction) of almost zero and a retardationof λ/4 or more relative to incident light incoming at a directioninclined from the normal direction by 30° or more,

layers (b2) each having a front retardation of about λ/4 disposed onboth sides of the layer (b1), one of the layers (b2) being disposedbetween the retardation layer (b1) and a corresponding linearpolarization type reflection polarizer (a2) and the other of the layers(b2) being disposed between the retardation layer (b1) and anotherlinear polarization type reflection polarizer (a2),

the layer (b2) on the incidence side is arranged at an angle of 45°(−45°)±5° relative to the polarization axis of the linear polarizationtype reflection polarizer (a2) on the incidence side,

the layer (b2) on the emission side is arranged at an angle of −45°(+45°)±5° relative to the polarization axis of the linear polarizationtype reflection polarizer (a2) on the emission side, and

the layer (b2) on the incidence side and the layer (b2) on the emissionside are arranged at an arbitrary angle formed between the respectiveslow axes thereof.

5. The viewing angle magnification liquid crystal display according toabove description 1 or 2, wherein

the reflection polarizer (a) is a linear polarization type reflectionpolarizer (a2) transmitting one of linearly polarized lightsperpendicular to each other, but selectively reflecting the otherthereof,

the retardation layer (b) comprises two biaxial retardation layers (b3)each having a front retardation (in the normal direction) of about λ/4and an Nz factor of 2 or more,

the slow axis direction of the layer (b3) on the incidence side isarranged at an angle of 45° (−45°)±5° relative to the polarization axisof the linear polarization type reflection polarizer (a2) on theincidence side,

the slow axis direction of the layer (b3) on the emission side isarranged at an angle of −45° (+45°)±5° relative to the polarization axisof the linear polarization type reflection polarizer (a2) on theemission side, and

the layer (b3) on the incidence side and the layer (b3) on the emissionside are arranged at an arbitrary angle formed between the respectiveslow axes thereof.

6. The viewing angle magnification liquid crystal display according toabove description 1 or 2, wherein

the reflection polarizer (a) is a linear polarization type reflectionpolarizers (a2) transmitting one of linearly polarized lightsperpendicular to each other, but selectively reflecting the otherthereof,

the retardation layer (b) comprises one biaxial retardation layer (b4)having a front retardation (in the normal direction) of about λ/2 and anNz factor of 1.5 or more,

the slow axis direction of the layer on the incidence side is arrangedat an angle of 45° (−45°)±5° relative to the polarization axis of thelinear polarization type reflection polarizer (a2) on the incidenceside,

the slow axis direction of the layer on the emission side is arranged atan angle of −45° (+45°)±5° relative to the polarization axis of thelinear polarization type reflection polarizer (a2) on the emission side,and

the polarization axes of the two linear polarization type reflectionpolarizers (a2) are almost perpendicular to each other.

7. The viewing angle magnification liquid crystal display according toany of above descriptions 1 to 4, wherein

the retardation layer (b1) is of a cholesteric liquid crystal phase,having a selective reflection wavelength band in a region outside thevisible light region, and fixed in a planar alignment state.

8. The viewing angle magnification liquid crystal display according toany of above descriptions 1 to 4, wherein

the retardation layer (b1) is of a rod-like liquid crystal fixed in ahomeotropic alignment state.

9. The viewing angle magnification liquid crystal display according toany of above descriptions 1 to 4, wherein

the retardation layer (b1) is of a discotic liquid crystal fixed in analignment state of a nematic phase or a columnar phase.

10. The viewing angle magnification liquid crystal display according toany of above descriptions 1 to 4, wherein

the retardation layer (b1) is a biaxially aligned polymer film.

11. The viewing angle magnification liquid crystal display according toany of above descriptions 1 to 4, wherein

the retardation layer (b1) is of an inorganic layered compound with anegative uniaxiality fixed in an alignment state so that the normaldirection of a surface of the compound is an optical axis.

12. The viewing angle magnification liquid crystal display according toany of above descriptions 3 and 6 to 11, wherein

the circular polarization type reflection polarizer (a1) comprises acholesteric liquid crystal.

13. The viewing angle magnification liquid crystal display according toany of above descriptions 3 and 6 to 12, wherein

a λ/4 plate is disposed on the viewer side (the liquid crystal cellside) of the circular polarization type reflection polarizer (a1), andan axis direction of a linearly polarized light obtained by transmissionand a transmission axis direction of a polarizing plate on the lowersurface side (the light source side) of the liquid crystal display aredisposed in alignment with each other.

14. The viewing angle magnification liquid crystal display according toany of above descriptions 4 to 11, wherein

the linear polarization type reflection polarizer (a2) is a stretchedresin laminate with multiple layers comprising resin materials havingrespective different refractive indexes and retardation.

15. The viewing angle magnification liquid crystal display according toany of above descriptions 4 to 11 and 14, wherein

an axis direction of a linearly polarized light obtained by transmissionof the linear polarization type reflection polarizer (a2) and atransmission axis direction of a polarizing plate on the lower surfaceside (the light source side) of the liquid crystal display are disposedin alignment with each other.

16. The viewing angle magnification liquid crystal display according toany of above descriptions 1 to 15, wherein

the viewing angle magnifying layer is a diffusion plate havingsubstantially neither backscattering nor polarization cancellation.

17. The viewing angle magnification liquid crystal display according toany of above descriptions 1 to 16,

wherein each of layers is laminated using a transparent adhesive agentor pressure-sensitive adhesive agent. (Action)

As described in the specification of U.S. Pat. No. 2,564,813 and thepublication of JP-A No. 10-321025, in a case where a retardation platecontrolled so that a retardation value in the vertically incidentdirection and a retardation value in an obliquely incident direction arespecially different from each other is inserted between polarizers, anangular distribution of transmitted light receives a constraint and withan absorption polarizer adopted, only light in the vicinity of the frontis transmitted, while peripheral light is all absorbed. On the otherhand, with a reflection polarizer used as the polarizer, only light inthe vicinity of the front is transmitted while peripheral light is allreflected. With such a theory adopted, emitted lights of the backlightcan be condensed and collimated without being accompanied by anabsorption loss.

Description will be given of the present invention together with amechanism of light condensation and brightness enhancement using anideal model as follows:

FIG. 1 is a descriptive representation showing a principle in a casewhere a circular polarization type reflecting polarizer (a1) is used asa reflecting polarizer (a). In FIG. 1, as a polarization element (A), acircular polarization type reflection polarizer (a1), a retardationlayer (b1) and a circular polarization type reflection polarizer (a1)are disposed in the order starting at the backlight side (the lowerside).

A working principle is as described in the steps 1) to 3):

1) With the circular polarization type reflection polarizer (a1)separating a polarized light by reflection, incident light is dividedinto transmitted light and reflected light by a rotational sense ofpolarization of incident light. Therefore, no absorption loss occurs.

2) With a special retardation plate (b1) having a front retardation ofalmost zero and a retardation in an oblique direction of a value, frontincident light passes as is.

3) Incident light in an oblique direction is not absorbed and returnedback as reflected light. The reflected light is repeatedly reflectedtill the light is converted to a transmitted light.

The retardation plate (b1) is generally referred to as a negative Cplate (negative retardation plate) or a positive C plate (positiveretardation plate). The retardation plates (b1) have properties that inthe vertical direction (the normal direction), a retardation is close tozero, while when being inclined, a retardation occurs. As typicalnegative C plates, exemplified are to be concrete: a biaxially stretchedpolycarbonate film and polyethylene terephthalate film, a film made of acholesteric liquid crystal, and having a selective reflection wavelengthband set to be shorter than visible light, a film made of a discoticliquid crystal aligned in parallel to a plane and a film made of aninorganic crystalline compound, having a negative retardation, andobtained by in-plane alignment. As a typical positive C plate,exemplified is, to be concrete: a liquid crystal film obtained inhomeotropic alignment.

A circular polarization type reflection polarizer (a1) in use is apolarizer in which a cholesteric liquid crystal is mainly aligned and atwist pitch is adjusted and fixed (for example, a laminate of pluralfilms having respective different selective reflection centralwavelengths or a film in a single layer and having a pitch altering inthe thickness direction) so that a selective reflection wavelength bandcovers a visible light region/a light source emission wavelength band;or the like. The circular polarization type reflection polarizers (a1)disposed on both sides of the retardation plate (b1) of FIG. 1 in useare preferably polarizers with the same rotational sense of transmittedcircularly polarized light as each other.

Since a circular polarization type reflection polarizer (a1) and theretardation plate (b1) can be used without designating an adherencedirection because of almost non-existence of axes in an in-planedirection for both. Hence, an angular range of confinement ofcollimation has isotropic/symmetrical characteristics.

Note that description below is given based on the figures; marks (r) areassigned as shown in FIG. 2 such that (i) indicate natural light, (ii)circularly polarized light and (iii) linearly polarized light. Thecircularly polarized light (ii) is divided into (ii)-1 and (ii)-2, whichhave respective arrow marks reverse in sense of rotation from eachother. This means that senses of rotation of both circularly polarizedlight are reverse to each other. The (iii)-1 and (iii)-2 mean thatpolarization axes of both are perpendicular to each other.

Description will be given of a case where the circular polarization typereflection polarizers (a1) shown in FIG. 1 are used as a reflectingpolarizer (a), following changes in lights in collimation.

1) Light vertically impinging on the circular polarization typereflection polarizer (a1) included in natural light supplied from abacklight is polarization separated into transmitted light (r3) andreflected light (r2). The transmitted light and the reflected light arereverse in rotational sense of circular polarization to each other.

2) The transmitted light (r3) passes through the retardation layer (b1)as is.

3) Transmitted light (r4) further passes through the circularpolarization type reflection polarizer (a1) as is.

4) Transmitted light (r5) is used in a liquid crystal display disposedthereon.

5) On the other hand, light obliquely impinging on the circularpolarization type reflection polarizer (a1) included in natural light(r6) supplied from the backlight is polarization separated intotransmitted light (r8) and a reflected light (r7). The transmitted lightand the reflected light are reverse in rotational sense of circularpolarization to each other.

6) Transmitted light (r8) is affected in retardation while passingthrough the retardation layer (b1). When retardation value of ½wavelength is given, circularly polarized light changes a currentrotational sense thereof to a reverse rotational sense. Hence, arotational sense of the transmitted light (r8) is inverted aftertransmission of the retardation layer (b1).

7) Transmitted light (r9) is emitted with a reverse rotational senseunder an influence of retardation.

8) The transmitted light (r9) with a reverse rotational sense isreflected back on the circular polarization type reflection polarizer(a1). It has been generally known that a rotational sense of acircularly polarized light is inverted when being reflected (W. A.Shurcliff, Polarized Light: Production and Use, (Harvard UniversityPress, Cambridge, Mass., 1966). As an exception, it has been known thatin a case of reflection on a cholesteric liquid crystal layer, no changein rotational sense occurs. Herein, since reflection is performed on acholesteric liquid crystal surface, no change occurs in either ofrotational senses of circular polarization of the transmitted light (r9)and the reflected light (r10).

9) The reflected light (r10) receives an influence of retardation whilepassing through the retardation layer (b1).

10) Transmitted light (r11) is inverted in rotational sense thereofunder an influence of retardation.

11) The transmitted light (r11) returns back with the same rotationalsense as the transmitted light (r8) because of inversion of a rotationalsense passes through the circular polarization type reflection polarizer(a1) as is.

12) Reflected light (r2, r7 and r12) returns back to the backlight sideand recycled. These returned light is repeatedly reflected till thelight changes propagation directions and a rotational sense ofpolarization at random by a diffusion plate and others disposed in thebacklight and thereby converted to light that can again transmit in thevicinity of the normal direction to a polarizer (A), therebycontributing to brightness enhancement.

13) Since the transmitted circularly polarized light (r5) can beconverted to linearly polarized light by disposing a λ/4 plate, thelight can be used in a liquid crystal display without causing absorptionloss.

In connection with a transmittance and reflectance of the circularpolarization type reflection polarizer (a1) using a cholesteric liquidcrystal, a wavelength characteristic of a transmitted light shifts tothe short wavelength side relative to incident light in an obliquedirection. Therefore, in order to function sufficiently on incidentlight at a deep angle, a necessity arises that a sufficient polarizationcharacteristic/retardation characteristic is ensured in the longwavelength side outside the visible light region. While the retardationlayer (b1) used in this system, ideally and theoretically, would haveonly to have a retardation of ½ wavelength, to be exact, in an obliquedirection, a circular polarization type reflection polarizer (al: acholesteric liquid crystal layer) actually used has a property as anegative retardation plate to some extent. Hence, the retardation layer(b1) can exert the optical function of the present invention if thelayer has a retardation of ⅛ wavelength or more in an oblique direction.

In a case where the reflection polarizer (a) is a linear polarizationtype reflection polarizer (a2), an optical axis relative to a lightincident a C plate in an oblique direction is always perpendicular to alight direction, for example, if the C plate (retardation layer (b1)) isused alone as a retardation layer. Hence, retardation is not produced tothereby cause no polarization conversion. Therefore, in a case where thelinear polarization type reflection polarizer (a2) is employed, λ/4plates (b2) each having the slow axis direction at an angle of 45° or−45° relative to the polarization axis of the linear polarization typereflection polarizer (a2) are disposed on both sides of the C plate.With such a construction applied, an operation can be performed that thelinearly polarized light is converted to a circularly polarized lightwith the λ/4 plate (b2), thereafter, the circularly polarized light isconverted to an inverted circularly polarized light by a retardation ofthe C plate and the circularly polarized light can be again converted tolinearly polarized light with the λ/4 plate (b2).

FIG. 3 is a conceptional view showing a process in which natural lightis polarization separated to a linearly polarized light with the linearpolarization type reflection polarizer (a2) and further converted tocircularly polarized light with the λ/4 plate (b2).

FIG. 4 is a conceptional representation in a case where a linearpolarization type reflection polarizer (a2) is employed as thereflection polarizer (a). In FIG. 4, as the polarizing element (A), alinear polarization type reflection polarizer (a2), a λ/4 plate (b2), aretardation layer (b1) and a linear polarization type reflectionpolarizer (a2) are disposed in the order starting at the backlight side(the lower side).

FIG. 5 is an example of laminate angles of respective films in acollimation system shown in FIG. 4. A double head arrow mark shown on alinear polarization type reflection polarizer (a2) is the polarizationaxis and a double head arrow mark shown on the λ/4 plate (b2) is theslow axis. Two pairs of the polarization axis of a linear polarizationtype reflection polarizer (a2) and the slow axis of a λ/4 plate (b2) arearranged on both sides of the C plate: the retardation layer (b1) so asto be at an angle of 45° (−45°)±5° relative to each other. Thecombinations are shown as set1 and set 2, respectively. Note that anangle formed between the axes of the λ/4 plates (b2) on the incidenceside and the emission side is arbitrary.

If an angle formed between a polarization axis of the linearpolarization type reflection polarizer (a2) and a slow axis of the λ/4plate (b2) is maintained at a value of 45° (−45°) relative to eachother, the set1 and the set2 may be rotated. Since the C plate: theretardation layer (b1) has no axis direction in a plane, the C plate canbe disposed without designation of an angle.

Description will be given, following changes in collimated lights shownin FIGS. 4 and 5.

1) Part of natural light (r14) supplied from a backlight verticallyimpinges on the linear polarization type reflection polarizer (a2).

2) The linear polarization type reflection polarizer (a2) transmitslinearly polarized light (r15) and reflects linearly polarized light(r16) in a direction perpendicular thereto.

3) The linearly polarized light (r15) transmits the λ/4 plate (b2) andis converted to circularly polarized light (r17).

4) The circularly polarized light (r17) passes through the retardationlayer (b1) as is.

5) Circularly polarized light (r18) passes through the λ/4 plate (b2)and is converted to linearly polarized light (r19).

6) The linearly polarized light (r19) passes through the linearpolarization type reflecting polarizer (a2) as is.

7) Linearly polarized light (r20) impinges on a liquid crystal displaydisposed thereon and transmitted through without a loss.

8) On the other hand, part of natural light (r21) supplied from thebacklight impinges obliquely on the linear polarization type reflectionpolarizer (a2).

9) The linear polarization type reflection polarizer (a2) transmits alinearly polarized light (r22) and reflects linearly polarized light(r23) in a direction perpendicular thereto.

10) The linearly polarized light (r22) transmits the λ/4 plate (b2) andis converted to circularly polarized light (r24).

11) The circularly polarized light (r24) is affected of a retardation of½ wavelength and a rotational sense thereof is inverted while passingthrough the retardation layer (b1).

12) Circularly polarized light (r25) with a reverse rotational sensepasses through the λ/4 plate (b2) and is converted to linearly polarizedlight (r26).

13) The linearly polarized light (r26) is reflected back on the linearpolarization type reflection polarizer (a2) and converted to linearlypolarized light (r27).

14) The linearly polarized light (r27) passes through the λ/4 plate (b2)and is converted to circularly polarized light (r28).

15) The circularly polarized light (r28) is affected of a retardation of½ wavelength and a rotational sense thereof is inverted while passingthrough the retardation layer (b1).

16) Circularly polarized light (r29) with a reverse rotational sensepasses through the λ/4 plate (b2) and is converted to linearly polarizedlight (r30).

17) The linearly polarized light (r30) passes through the linearpolarization type reflection polarizer (a2) as is.

18) Reflected light (r16, r23 and r31) returns back to the backlightside and recycled.

While in an ideal system, an angle between the slow axis of a λ/4 plate(b2) described herein and the polarization axis of a linear polarizationtype reflection polarizer (a2) theoretically in essence is 45°,characteristics of the linear polarization type reflection polarizer(a2) and the λ/4 plate (b2) in a practical case are not perfect in thevisible light region and each have a subtle change according to awavelength. If this is neglected and lamination is conducted at 45°,there arises a case where coloration occurs.

Therefore, by shifting an angle slightly to compensate a hue,optimization of the system in the entirety can be reasonably realized.On the other hand, if an angle is largely shifted, there arise otherproblems such as reduction in transmittance and others. Therefore, it isdesirable that adjustment is actually performed within a range of theorder of ±5°.

In connection with a transmittance and reflectance of the linearpolarization type reflection polarizer (a2), that a wavelengthcharacteristic of a transmitting light shifts relative to incident lightin an oblique direction to the short wavelength side is the same as inthe circular polarization type reflection polarizer (a1) using acholesteric liquid crystal. Therefore, in order to function sufficientlyon incident light at a deep angle, a necessity arises that a sufficientpolarization characteristic/retardation characteristic is ensured in thelong wavelength side outside the visible light region.

The linear polarization type reflection polarizer (a2) has a smallernegative retardation characteristic of its own as compared with that ofa cholesteric liquid crystal. Therefore, a retardation in an obliquedirection (an inclination of 30°) of the retardation layer (b1) used bybeing inserted between the linear polarization type reflectionpolarizers (a2) is somewhat larger than in the case of the circularpolarization type reflection polarizers (a1) using a cholesteric liquidcrystal and preferably ¼ wavelength or more.

In a case where the reflection polarizer (a) is the linear polarizationtype reflection polarizer (a2), which is different from the abovedescribed case, a similar effect can also be obtained by replacing thestructure in which the C plate: the retardation layer (b1) is sandwichedbetween the two λ/4 plates (b2) with two biaxial retardation layers (b3)each of which has a front retardation of about λ/4, and a retardation inthe thickness direction of about λ/2 or more. Such a biaxial retardationlayer (b3) with an Nz factor of 2 or more satisfies the above describedrequired conditions.

FIG. 6 is a conceptional representation in a case where the linearpolarization type reflection polarizers (a2) are adopted as reflectionpolarizers (a) and the biaxial retardation layers (b3) is employed. InFIG. 6, as a polarization element (A), a linear polarization typereflection polarizer (a2), a biaxial retardation layer (b3), a biaxialretardation layer (b3) and a linear polarization type reflectionpolarizer (a2) are disposed in the order starting at the backlight side(the lower side).

FIG. 7 is an example of laminate angles of films in the collimationsystem shown in FIG. 6. A double head arrow mark shown on a linearpolarization type reflection polarizer (a2) is the polarization axis; adouble head arrow shown on a retardation layer (b1) is the slow axis.The polarization axis of a linear polarization type reflection polarizer(a2) and the slow axis of a biaxial retardation layer (b3) are arrangedat an angle of 45° (−45°)±5° therebetween. The combinations areindicated by set 1 and set 2, respectively.

For ease in description of optical paths, there is exemplified a casewhere the linear polarization type reflection polarizers (a2) disposedone above the other have the respective polarization axes parallel toeach other and slow axes of the two biaxial retardation layers (b3) oneon the other are perpendicular to each other. The biaxial retardationlayers (b3) one on the other has the respective slow axes forming anarbitrary angle therebetween. The set 1 and set 2 may be rotated as faras an angle between the polarization axis of a linear polarization typereflection polarizer (a2) and the slow axis of a biaxial retardationlayer (b3) is maintained at a value of 45° (−45°) relative to eachother.

Description will be given, following changes in collimated lights shownin FIGS. 6 and 7.

1) Part of natural light (r32) supplied from a backlight impingesvertically on the linear polarization type reflection polarizer (a2).

2) The linear polarization type reflection polarizer (a2) transmitslinearly polarized light (r33) and reflects linearly polarized light(r34) in a direction perpendicular to the linearly polarized light(r33).

3) The linearly polarized light (r33) transmits the two biaxialretardation layers (b3) each with a front retardation of about ¼wavelength. Herein, since the slow axes of the two biaxial retardationlayers (b3) one on the other are perpendicular to each other at 90°, thefront retardation is 0. Therefore, linearly polarized light (r35) passesthrough as is.

4) The linearly polarized light (r35) passes through the linearpolarization type reflection polarizer (a2) as is.

5) Linearly polarized light (r36) impinges on a liquid crystal displayand transmitted without a loss.

6) On the other hand, part of natural light (r37) supplied from thebacklight impinges obliquely on the linear polarization type reflectionpolarizer (a2).

7) The linear polarization type reflection polarizer (a2) transmitslinearly polarized light (r38) and reflects linearly polarized light(r39) in a direction perpendicular to thereof.

8) The linearly polarized light (r38) impinges obliquely on the twobiaxial retardation layers (b3). Since the two biaxial retardationlayers (b3) each have a front retardation of ¼ wavelength and an Nzfactor of 2 or more, linearly polarized light (r40) transmitted throughthe two biaxial retardation layers (b3) changes the polarization axisdirection thereof by 90° because of a change in retardation in thethickness direction.

9) Linearly polarized light (r40) impinges on the linear polarizationtype reflection polarizer (a2).

10) Since the linear polarization type reflection polarizers (a2) oneabove the other have the polarization axes in the same direction, thelinearly polarized light (r40) is reflected as a reflected light (r41).

11) The reflected light (r41) is affected of a retardation while passingthrough the two biaxial retardation layers (b3) in a similar way to thatin the step 8) to thereby form linearly polarized light (r42) with thepolarization axis direction thereof rotated by 90°.

12) The linearly polarized light (r42) passes through the linearpolarization type reflection polarizer (a2) as is.

13) Reflected light (r34, r39 and r43) returns back to the backlightside and recycled.

The polarization element (A) shown in FIGS. 6 and 7 have the two biaxialretardation layers (b3), having a front retardation of about ¼wavelength and an Nz factor of 2 or more, laminated one on the othereach. This structure can produces almost the same characteristic as inthe case employing a three layered laminate of the structure in whichthe C plate : the retardation layer (b1) is sandwiched between the twoλ/4 plates (b2), which is shown in FIGS. 4 and 5. Therefore, the numberof laminated layers is smaller and productivity is somewhat moreexcellent than the above described polarization element (A).

While in an ideal system, an angle between the slow axis of aretardation plate (b3) and the polarization axis of a linearpolarization type reflection polarizer (a2) described hereintheoretically in essence is 45°, characteristics of the linearpolarization type reflection polarizer (a2) and the retardation layer(b3) in a practical case are not perfect in the visible light region andeach have a subtle change according to a wavelength. If this isneglected and lamination is conducted at 45°, there arises a case wherecoloration occurs.

Therefore, by shifting an angle slightly to compensate a hue,optimization of the system in the entirety can be reasonably realized.On the other hand, if an angle is largely shifted, there arises a casewhere other problems such as reduction in transmittance and othersoccur. Therefore, it is desirable that adjustment is actually performedwithin a range of the order of ±5°.

In connection with a transmittance and reflectance of the linearpolarization type reflection polarizer (a2), that a wavelengthcharacteristic of transmitted light shifts relative to incident light inan oblique direction to the short wavelength side is the same as thecircular polarization type reflection polarizer (a1) using a cholestericliquid crystal. Therefore, in order to function sufficiently on incidentlight at a deep angle, a necessity arises that a sufficient polarizationcharacteristic/retardation characteristic is ensured in the longwavelength side outside the visible light region.

In a case where a reflection polarizer (a) is a linear polarization typereflection polarizer (a2), a similar effect can also be obtained bydisposing a biaxial retardation layer (b4) having a front retardation ofabout λ/2 and a retardation in the thickness direction of λ/2 or more asa retardation layer (b). Such a biaxial retardation layer (b4) with anNz factor of 1.5 or more satisfies the above described requiredconditions.

FIG. 8 is a conceptional representation in a case where a linearpolarization type reflection polarizer (a2) is employed as a reflectionpolarizer (a). In FIG. 8, as the polarization element (A), a linearpolarization type reflection polarizer (a2), a biaxial retardation layer(b4) and a linear polarization type reflection polarizer (a2) aredisposed in the order starting at the backlight side (the lower side).

FIG. 9 is an example of laminate angles of films in the collimationsystem shown in FIG. 8. A double head arrow mark shown on a linearpolarization type reflection polarizer (a2) is the polarization axisand, a double head arrow shown on a retardation layer (b4) is the slowaxis. The polarization axes of the linear polarization type reflectionpolarizer (a2) one above the other are arranged so as to beperpendicular to each other. The slow axis of a biaxial retardationlayer (b4) and the polarization axis of a linear polarization typereflection polarizer (a2) are arranged at an angle of 45° (−45°)±5°therebetween.

Description will be given, following changes in collimated lights in theabove described example shown in FIGS. 8 and 9.

1) Part of natural light (r47) supplied from a backlight impingesvertically on the linear polarization type reflection polarizer (a2).

2) The linear polarization type reflection polarizer (a2) transmitslinearly polarized light (r48) and reflects linearly polarized light(r49) in a direction perpendicular to the linearly polarized light(r48).

3) The linearly polarized light (r48) transmits the biaxial retardationlayer (b4) with a front retardation of about ½ wavelength and convertedto linearly polarized light (r50) and a direction of the polarizationaxis thereof is rotated by 90°.

4) The linearly polarized light (r50) passes through the linearpolarization type reflection polarizer (a2) as is.

5) Transmitted linearly polarized light (r51) impinges on a liquidcrystal display and is transmitted without a loss.

6) On the other hand, part of natural light (r52) supplied from thebacklight impinges obliquely on the linear polarization type reflectionpolarizer (a2).

7) The linear polarization type reflection polarizer (a2) transmitslinearly polarized light (r53) and reflects linearly polarized light(r54) in a direction perpendicular to the linearly polarized light(r53).

8) The linearly polarized light (r53) impinges obliquely on the biaxialretardation layer (b4). Since the biaxial retardation layer (b4) has afront retardation of about ½ wavelength and an Nz factor of 2 or moredue to the effect of the retardation in the thickness direction, thelinearly polarized light (r53) transmits the biaxial retardation layer(b4) as a linearly polarized light (r55) in the same state as thelinearly polarized light (r53) with respect of a direction of thepolarization axis.

9) Transmitted linearly polarized light (r55) is reflected on the linearpolarization type reflection polarizer (a2) and converted to reflectedlight (r56).

10) The reflected light (r56) impinges on the retardation layer (b4). Onthis occasion, the reflected light (r56) transmits without altering theaxis direction.

11) Transmitted linearly polarized light (r57) passes through the linearpolarization type reflection polarizer (a2) as is, as linearly polarizedlight (r58).

12) Reflected light (r49, r54 and r58) returns back to the backlightside and recycled.

The polarization element (A) shown in FIGS. 8 and 9 include the singlebiaxial retardation layer (b4) having a front retardation of about ½wavelength and an Nz factor of 1.5 or more. This structure can producealmost the same characteristic as in the case where the three layeredlaminate in a structure in which the C plate: the retardation layer (b1)is sandwiched between the two λ/4 plates (b2), which is shown in FIGS. 4or 5. Therefore, the number of layers in the laminate is less andsomewhat more excellent in productivity as compared with those of theabove described polarization element (A). Moreover, the polarizationelement (A) shown in FIGS. 8 and 9 is more excellent than the case wherea two layer laminate is used as sown in FIGS. 6 and 7.

While in an ideal system, an angle between the slow axis of theretardation plate (b4) and the polarization axis of a linearpolarization type reflection polarizer (a2) described hereintheoretically in essence is 45°, characteristics of the linearpolarization type reflection polarizer (a2) and the retardation plate(b4) in a practical case are not perfect in the visible light region andeach have a subtle change according to a wavelength. If this isneglected and lamination is conducted at 45°, there arises a case wherecoloration occurs.

Therefore, by shifting an angle slightly to compensate a hue,optimization of the system in the entirety can be reasonably realized.On the other hand, if an angle is largely shifted, there arises a casewhere other problems such as reduction in transmittance and othersoccur. Therefore, it is desirable that adjustment is actually performedwithin a range of the order of ±5°.

In connection with a transmittance and reflectance of the linearpolarization type reflection polarizer (a2), that a wavelengthcharacteristic of a transmitted light shifts relative to incident lightin an oblique direction to the short wavelength side is the same as thecircular polarization type reflection polarizer (a1) using a cholestericliquid crystal. Therefore, in order to function sufficiently on incidentlight at a deep angle, a necessity arises that a sufficient polarizationcharacteristic/retardation characteristic is ensured in the longwavelength side outside the visible light region.

A polarization element (A), as shown in FIGS. 1 to 9, has a retardationlayer (b) converting light impinging at an incidence angle of 30°inclined from the normal direction to polarized light with an axisdirection to be reflected by two reflection polarizers (a) and thepolarization element (A) functions a total reflection at an incidenceangle of 30° not to transmit light at an incidence angle close to 30°.The polarization element (A) has a substantially high transmittance atan incidence angle in the range of the order of from ±15° to ±20°inclined from the normal direction while light at an incidence anglehigher than the range is reflected and recycled. Hence, transmittedlights from a light source are concentrated in the above range andcondensed and collimated.

Thus obtained beam collimated backlight, as features thereof, is thinnerand makes a light source with a high light parallelism to be obtainedwith more of ease than in a conventional practice. In addition, sincecollimation is realized by polarizing reflection substantially withoutabsorption loss, reflected non-collimated light component returns to thebacklight side and scattering reflected, wherein only a collimated lightcomponent of the scattered reflected light is extracted for recycling,which process is repeated, thereby enabling a substantially hightransmittance and a substantially high light utilization efficiency tobe achieved.

As a collimated light diffusing means, preferably used is a diffusionplate described in the specifications of JP-A Nos. 2000-347006 and2000-347007 having low backscattering. In this case, a viewing angle ismagnified isotropically so that there is observed no difference betweenviewing angle characteristics of images in upper and lower portions ofthe screen or in right and left portions thereof. A liquid crystaldisplay having such a characteristic is preferably employed in any ofapplications to DTP, a digital camera, a video camera and others, whichare in more of cases used by changing a facing direction of the liquidcrystal display in every direction when viewed therethrough.

Since with employment of a diffusion plate having anisotropy in lightdiffusibility as observed in a hologram material or a microlens arraysheet controlled in shape anisotropy, a viewing angle characteristic ina direction, from left to right, and a downward direction can beselectively improved, the diffusion plate or the sheet is preferablyused in application to a television set with a horizontally long screen.

A retardation anisotropy control type collimating means used in thisinvention is characterized by that no in-plane fine structure isvisually recognized when being viewed along a surface direction inoptical observation, absolutely no interference is observed betweenliquid crystal pixels, a black matrix, a film having a fine structureused in a collimating means, a glare-treated surface as the outermostsurface of the liquid crystal display and others, which fine structuresare no cause for a moiré.

A moiré, shown in FIG. 10, is a pattern of darkness and brightnesshaving a frequency lower than that of a lattice visually recognized whenlayers are superimposed with lattices formed in the respective differentlayers at angles therebetween.

A pitch of a moiré stripe is expressed by the following formula 1:

$\left( \frac{1}{S3} \right)^{2} = {\left( \frac{1}{S1} \right)^{2} + \left( \frac{1}{S2} \right)^{2} - \frac{2\cos\;\alpha}{{S1} \times {S2}}}$In the formula 1, S1 indicates a first lattice pitch, S2 a secondlattice, S3 a moiré fringe pitch and α an angle formed between the firstlattice and the second lattice.

If a visibility (V) of a moiré stripe is calculated with definition ofthe maximum value of intensities I of a moiré stripe obtained bysuperimposing different lattices in such a way as Imax, the minimumvalue thereof as Imin, the visibility is given by a mathematicalexpression: V=(Imax−Imin)/(Imax+Imin). In order to decrease thecontrast, it is desirable that an angle between the lattices issufficiently large and close to perpendicularity. Three or more layerseach having a lattice is hard to satisfy the required condition.Therefore, in order to suppress a moiré phenomenon, it is effective toreduce layers each having a lattice structure and it is understood thata polarization element of this invention with no lattice structure isgreatly effective for manufacture of a viewing angle magnificationsystem.

A thin film layer producing collimated lights has a thickness at a levelin the range of from tens to hundreds of μm including even a reflectionpolarizer, which makes it easy to design an extremely thin type ascompared with a prism array or microlens sheets. Since an air interfacedoes not require, adherence of layers is enabled, leading to a greatadvantage obtained in handling. For example, in a case where employed isa cholesteric liquid crystal polymer (about 10 μm) as a reflectionpolarizer, retardation plates used in combination are coated thin films(about 5 μm) made of a liquid crystal polymer and if the films arelaminated with an adhesive agent (about 5 μm), a total thickness can bethinned to 50 μm or less. A further thinner layer composite can berealized if the layers are directly coated without interfaces.

EFFECT OF THE INVENTION

A viewing angle magnification liquid crystal display of this inventioncondenses emitted lights only in view fields each having the highestcontrast and good color reproducibility. As a result, a picture imageobtained from the liquid crystal display can be brighter only in viewfields good in display quality.

As for a thickness, a functional film realizing collimation is 200 μm orless and if a thickness of a support base material used in manufactureis excluded, an optical film with a practically sufficient performanceis obtained on the order of tens of μm. This thickness range has notbeen realized with a material for geometric optics such asconventionally used lens, prism and others. That is, this is a greatadvantage as compared with a viewing angle magnification system havingbeen conventionally proposed.

Adoption of this system to make uniform lights with good displaycharacteristic in a region in the vicinity of the front and to magnify aview angle enables a liquid crystal display high in durability to grayscale inversion and a change in hue and good in viewing anglecharacteristic to be obtained. In this system, a cell of the liquidcrystal display acquires a sufficiently high characteristic even in acase where no compensation film is applied to an ordinary TN liquidcrystal that has been conventionally available and no necessity arisesfor liquid crystal alignment control or a special retardation plateprovided at high cost.

According to a viewing angle magnification liquid crystal display ofthis invention, a thin type viewing angle magnification system, whichhas not been conventionally available, can be, in such a way, realizedwith ease at a low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptional representation showing an example of thefundamental principle for collimation of a polarization element (A).

FIG. 2 is diagrams describing each of the states of lights in FIGS. 1,3, 4, 6 and 8.

FIG. 3 is a conceptional view showing conversion of linearly polarizedlight to circular polarization.

FIG. 4 is a conceptional representation showing an example of thefundamental principle of collimation of a polarization element (A).

FIG. 5 is an example showing arrangement angles of each of the layersfor collimation using a linear polarization type reflecting polarizationelement (a2).

FIG. 6 is a conceptional representation showing an example of thefundamental principle for collimation of a polarization element (A).

FIG. 7 is an example showing arrangement angles of each of the layersfor collimation using a linear polarization type reflecting polarizationelement (a2).

FIG. 8 is a conceptional representation showing an example of thefundamental principle for collimation of a polarization element (A).

FIG. 9 is an example showing arrangement angles of each of the layersfor collimation using a linear polarization type reflecting polarizationelement (a2).

FIG. 10 is a conceptional representation showing a direct solution of amoiré.

FIG. 11 is a conceptional view of a viewing angle magnification liquidcrystal display of a first embodiment.

FIG. 12 is a conceptional view of a viewing angle magnification liquidcrystal display of a second embodiment.

FIG. 13 is a conceptional view of a viewing angle magnification liquidcrystal display of a third embodiment.

FIG. 14 is a conceptional view of a viewing angle magnification liquidcrystal display of a fourth embodiment.

FIG. 15 is a conceptional view of a viewing angle magnification liquidcrystal display of a fifth embodiment.

FIG. 16 is a conceptional view of a viewing angle magnification liquidcrystal display of a sixth embodiment.

FIG. 17 is a conceptional diagram showing a relationship between axes onlaminated layers of a two layer broad band λ/4 retardation plates (b2)with respective different axes in a seventh embodiment.

FIG. 18 is a conceptional view of a viewing angle magnification liquidcrystal display of the seventh embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Illustrations of preferred embodiments of a viewing angle magnificationliquid crystal display of the present invention are below as shown inFIGS. 11 to 16 and 18.

A polarization element (A) of this invention can be formed by insertinga retardation layer (b) showing the special values of a frontretardation and a retardation relative to obliquely incident lightbetween at least two reflection polarizers (a) having respectiveselective reflection wavelength bands of polarized light superimposed oneach other to thereby superimpose the layers physically on each other.

With such a construction adopted, part of light transmitted obliquelythrough a reflection polarizer on the incidence side can be totallyreflected by a reflection polarizer on the emission side. With thiseffect, a liquid crystal display disposed on a backlight light source bywhich light condensation and collimation are performed can use lightsonly in a region in the vicinity of the front and high in displayquality to thereby spread lights good in display quality using a lightdiffusing means for magnification of a viewing angle disposed on theviewer side and to enable a viewing angle magnification system to beformed.

(Reflection Polarizer (a))

It is desirable to achieve a total reflection of light with a wavelengthin the vicinity of 550 nm high in visual sensitivity from the viewpointof brightness enhancement and it is desirable that a selectivereflection wavelength of the reflection polarizer (a) is superimposed onlight at least in a wavelength region of 550 nm ±10 nm.

In a backlight using a wedge type light guide plate adopted in more ofliquid crystal displays, for example, angles of emitted lights from thelight guide plate are about 60° inclined from the normal direction. Ablue shift amount at this angle reaches about 100 nm. Therefore, it isunderstood that in a case where a 3 wavelength cold cathode fluorescentlamp is employed as the backlight, a necessity arises that a selectivereflection wavelength reaches to the wavelength side longer than atleast 710 nm since a red bright-line spectrum is at 610 nm. Since aselective reflection wavelength bandwidth necessary in the longwavelength side, as described above, depends largely on an incidenceangle and a wavelength of incident light from the light source, a longwavelength end thereof is set arbitrarily according to requiredspecifications.

In a case where the backlight light source emits only a specificwavelength, for example, in a case of a colored cold cathode fluorescentlamp, it is only required to enable only an obtained bright line to beshielded.

In a case where emitted lights from the backlight are confined in arange in the front direction in advance in design of a microlens, dots,a prism, and others, it is not necessary to remarkably extend aselective reflection wavelength to the long wavelength side sincetransmitted light at a large incidence angle can be neglected. A designcan be affected properly so as to be adapted for combined members and akind of light source.

The reflection polarizers (a) may be either a combination of absolutelythe same members or a combination of one member reflecting all thewavelengths of visual light thereon and the other reflecting partthereof thereon.

(Circular Polarization Type Reflection Polarizer (a1))

For example, a cholesteric liquid crystal material is used in a circularpolarization type reflection polarizer (a1). In a circular polarizationtype reflection polarizer (a1), a central wavelength in selectivereflection is determined by a formula λ=np (wherein n indicates arefractive index of a cholesteric material and p indicates a chiralpitch). For obliquely incident light, the superimposed wavelength regionis preferably wider since a selective reflection wavelength is subjectedto a blue shift.

In a case where a circular polarization type reflection polarizer (a1)is made of a cholesteric materials, a similar polarizer can be obtainedeven in combination of different types (which are of a right hand twistand a left hand twist) in a way such that according to a similar way ofthinking, a retardation is zero or λ if a front retardation is inclinedat λ/2, whereas the similar polarizer is unprofitable since a problemarises because of anisotropy or coloring abnormality according to anazimuth of the inclined axis. While from such a viewpoint, it ispreferable to combine members of the same type (between only memberswith a right hand twist or only members with a left hand twist),coloring abnormality can also be suppressed by cancellation withcombination of cholesteric liquid crystal molecules one above the otheror a C plate different in wavelength distribution characteristic fromeach other.

A proper cholesteric liquid crystal may be used as a cholesteric liquidcrystal constituting a circular polarization type reflection polarizer(a1) without imposing any specific limitation. Examples thereof that arenamed include: a liquid crystal polymer exhibiting a cholesteric liquidcrystallinity at a high temperature; a polymerized liquid crystalobtained by polymerizing a liquid crystal monomer, and a chiral agentand an alignment agent, when both are required, with illumination ofionizing radiation such as an electron beam, ultraviolet or the like, orwith heating; and a mixture thereof. While a liquid crystallinity may beeither lyotropic or thermotropic, a thermotropic liquid crystal isdesirable from the view point of ease of control and formability ofmonodomain.

Formation of a cholesteric liquid crystal layer can be performed bymeans of a method in conformity with a conventional alignment treatment.Exemplified are: a method in which a liquid crystal polymer is developedon a proper alignment film selected from the group: an alignment filmobtained by being subjected to a rubbing treatment with a rayon cloth orthe like on a film made of polyimide, polyvinyl alcohol, polyester,polyarylate, polyamide imide, polyether imide or the like formed on asupport base material having as low a birefringence retardation aspossible such as triacetyl cellulose, amorphous polyolefin or the like;an alignment film made of an obliquely evaporated layer made of SiO₂; analignment film made of a base material using a surface nature and stateof a stretched base material such as polyethylene terephthalate,polyethylene naphthalate or the like; an alignment film made of a basematerial with fine surface irregularity of projections and depressionshaving a fine alignment control force formed thereon obtained bytreating a surface thereof with a fine grinding agent represented by arubbing cloth or red iron oxide; an alignment film made of a basematerial having an alignment film producing a liquid crystal controlforce by illuminating an azobenzene compound or the like on a basematerial film described above with light formed thereon; and others, andthe liquid crystal polymer is heated at a temperature of a glasstransition temperature or higher and lower than an isotropic phasetransition temperature and cooled at a temperature lower than the glasstransition temperature in a planar alignment state of the liquid crystalpolymer molecules into a glassy state to thereby form a fixed layer inwhich the alignment is fixed; and other methods.

A structure may also be fixed by illuminating with energy such asultraviolet, an ion beam or the like at a stage where an alignment stateis established. A base material with a low birefringence of the abovedescribed base materials may also be used as a liquid crystal layersupport as is. In a case where a base material with a high birefringenceis adopted or where a request for a thickness of a polarization element(A) is severe, a liquid crystal layer can be separated from thealignment base material for proper use.

Film formation of a liquid crystal polymer can be performed by means ofa method in which a liquid crystal polymer is developed into a thin filmusing a solution of the liquid crystal polymer with a solvent with oneof the following techniques: such as a spin coating method; a rollcoating method, a flow coating method; a printing method; a dip coatingmethod; a flow film forming method; a bar coating method; a gravureprinting method and others, to further dry the thin film, when required.Examples of the solvent that can be properly used include: chlorinecontaining solvents such as methylene chloride, trichloroethylene andtetrachloroethane; ketone solvents such as acetone, methyl ethyl ketoneand cyclohexanone; aromatic solvents such as toluene; cycloalkanes suchas cycloheptane; and N-methylpyrrolidone, tetrahydrofuran and others.

One of methods can be adopted in which a heat-melt of a liquid crystalpolymer and preferably a heat-melt in a state exhibiting an isotropicphase is developed in a procedure in conformity with a procedure asdescribed above, the developed film is further developed to a thinnerfilm while a melting temperature is maintained, if necessary, and thethinner film is then solidified. The one method is a method using nosolvent; therefore, a liquid crystal polymer can be developed by amethod good in hygiene in a working environment as well. Note that indevelopment of a liquid crystal polymer, there can be adopted asuperimposition scheme for cholesteric liquid crystal layers withalignment films interposed between layers for the purpose to realize athinner, if necessary.

One of the optical layers can also be separated from a support basematerial/an alignment base material therefore used in film formation andtransferred onto another optical material for use when required.

(Linear Polarization Type Reflection Polarizer (a2))

Examples of the liner polarization type reflection polarizer (a2)include: a grid type polarizer; a multilayer thin film laminate with twoor more layers made of two or more kinds of materials having adifference between refractive indexes; evaporated multilayer thin filmhaving different refractive indexes used in a beam splitter or the like;a multi-birefringence layer thin film laminate with two or more layersmade of two or more kinds of materials each having birefringence; astretched resin laminate with two or more layers using two or more kindsof resins each having a birefringence; a polarizer separating linearlypolarized light by reflecting/transmitting linearly polarized light inthe axis directions perpendicular to each other; and others.

A uniaxially stretched multilayer laminate can be used that is obtainedby uniaxially stretching a multilayer laminate obtained by alternatelylaminating materials generating a retardation by stretching representedby polyethylene naphthalate, polyethylene terephthalate andpolycarbonate; and resins each generating a low retardation, such as anacrylic resin represented by polymethacrylate; and a norbornene resinand others represented by ARTON manufactured by JSR Corp.

(Retardation Layer (b))

The retardation layer (b1) inserted between circular polarization typereflection polarizers (a1) or linear polarization type reflectionpolarizers (b2) has a retardation in the front direction of almost zeroand a retardation of λ/8 or more relative to incident light at an angleof 30° inclined from the normal direction. It is desirable to have afront retardation of λ/10 or less since it is the purpose to retainvertically impinging polarized light.

Retardation relative to incident light in an oblique direction isproperly determined according to an angle at which total reflection iseffected for efficient polarization conversion. In order to perfectlyrealize total reflection at an angle of the order of 60° inclined fromthe normal direction, it is only required to determine a retardation soas to be a value of the order of λ/2 when measured at 60°. Sincetransmitted light through the circular polarization type reflectionpolarizer (a1) changes a polarization state thereof by a birefringencelike a C plate of the circular polarization type reflection polarizer(a1) itself as well, a retardation when measured at the angle of the Cplate that is usually inserted may be a value less than λ/2. Since aretardation of the C plate increases monotonously with increase ininclination of incident light, a retardation has only to be λ/8 or morerelative to incident light at an angle of 30° as a target value foreffectively causing total reflection at inclination at an angle of 30°or more.

In a case of a design capable of an effective shield of light having anincidence angle of 30° from the front in a polarization element (A) ofthis invention, transmitted light is sufficiently reduced substantiallyin a region of an incidence angle of about 20°. In a case where light islimited in this region, transmitted is only light in a region showing agood display of a common TN liquid crystal display. There is afluctuation due to a kind of liquid crystal in a cell, a condition of analignment state, a pretilt angle and the like in a used TN liquidcrystal display, neither gray scale inversion nor sudden degradation incontrast occurs; therefore, this is a standard adopted for magnificationof a viewing angle in this invention. Other contrivances may also beapplied that a larger retardation value of a retardation layer is usedin order to confine only front light and that milder confinement isgiven with a smaller retardation value in a particular situation where acompensating retardation plate is combined with a TN liquid crystal.

Any of materials can be used in the retardation layer (b1) without aspecific limitation as far as it has an optical characteristic asdescribed above. Exemplified are: a layer having a fixed planaralignment state of a cholesteric liquid crystal having a selectivereflection wavelength in a region outside a visible light region(ranging from 380 nm to 780 nm); a layer having a fixed homeotropicalignment state of a rod-like liquid crystal; a layer using columnaralignment or nematic alignment of a discotic liquid crystal; a layer inwhich a negative uniaxial crystal is aligned in a plane; a layer made ofa biaxially aligned polymer film; and others.

As for a C plate, for example, a C plate having a fixed planar alignmentstate of a cholesteric liquid crystal having a selective reflectionwavelength in a region outside the visible light region (ranging from380 nm to 780 nm) is desirable to have no coloring abnormality in thevisible light region with respect to a selective reflection wavelengthof a cholesteric liquid crystal. Hence, a necessity arises for aselective reflection light not to be in the visible region. Selectivereflection is specially determined by a cholesteric chiral pitch and arefractive index of a liquid crystal. A value of a central wavelength inselective reflection may be in the near infrared region, whereas it ismore desirably in an ultraviolet region of 350 nm or less because of aninfluence of optical rotation exerted or occurrence of a slightlycomplex phenomenon. Formation of a cholesteric liquid crystal layer isperformed in a similar way to that in formation of a cholesteric liquidcrystal layer in the reflection polarizer described above.

A C plate having a fixed homeotropic alignment state is made of a liquidcrystalline thermoplastic resin showing a nematic liquid crystallinityat a high temperature; a polymerized liquid crystal obtained bypolymerizing a liquid crystal monomer and an alignment agent, whenrequired, under illumination with ionizing radiation such as an electronbeam, ultraviolet or the like, or with heating; or a mixture thereof.While a liquid crystallinity may be either lyotropic or thermotropic, athermotropic liquid crystal is desirable from the view point of ease ofcontrol and formability of monodomain. A homeotropic orientation isobtained for example in a procedure in which a birefringent materialdescribed above is coated on a film made of a vertically aligned film(such as a film of a long chain alkylsilane) and a liquid crystal stateis produced and fixed in the film.

As a C plate using a discotic liquid crystal, there is available a plateobtained by producing and fixing a nematic phase or a columnar phase ina discotic liquid crystal material having an optically negativeuniaxiality such as a phthalocyanines or a triphenylene compounds eachhaving an in-plane spread molecule as a liquid crystal material.Inorganic layered compounds each with a negative uniaxiality aredetailed in a publication of JP-A No. 6-82777 and others.

A C plate using a biaxial alignment of a polymer film can be obtained byone of the following methods, in which a polymer film having positiverefractive index anisotropy is biaxially stretched in a good balance; inwhich a thermoplastic resin is pressed; and in which a C plate is cutoff from a parallel aligned crystal.

In a case where a linear polarization type reflection polarizer (a2) isemployed, adopted is a retardation layer (b1) having retardation in thefront direction of almost zero and a retardation of λ/4 or more relativeto incident light incoming at an angle of 30° inclined from the normaldirection. Linearly polarized light is converted to circularly polarizedlight using a structure in which the retardation layer (b1) issandwiched between λ/4 plates (b2) each having a front retardation ofabout λ/4 and thereafter, the circularly polarized lights can becollimated by means of a similar way to that in the circular polarizingplate described above. A section of the structure and arrangement oflayers thereof in this case are as shown in FIGS. 3, 4 and 5. In thecase, an angle formed between the slow axis of a λ/4 plate (b2) and thepolarization axis of a linear polarization type reflection polarizer(a2) is as described above and an angle between the axes of the λ/4plates (b2) can be arbitrarily set.

To be concrete, a λ/4 plate is used as the retardation layer (b2). A λ/4plate in use is a proper retardation plate adapted for a purpose of use.The λ/4 plate can control an optical characteristic such as aretardation in lamination of two or more kinds of retardation plates.Examples of retardation plates include: birefrengent films obtained bystretching films made of proper polymers such as polycarbonate,norbornene resin, polyvinyl alcohol, polystyrene,polymethylmethacrylate, polypropylene, other polyolefins, polyarylate,polyamide and others; alignment films each made of a liquid crystalmaterial such as a liquid crystal polymer; alignment layers each made ofa liquid crystal material supported by a film; and others.

A retardation plate functioning as a λ/4 plate in a broad wavelengthrange such as the visible light region can be obtained by a method inwhich, for example, a retardation layer functioning as a λ/4 plate formonochromatic light with a wavelength of 550 nm, a retardation layerexhibiting another retardation characteristic, for example a retardationlayer functioning as a ½ wavelength plate are superimposed one on theother, or the like method. Therefore, a retardation plate insertedbetween a polarizing plate and a brightness enhancement film may be madewith one, or two or more retardation layers.

A similar effect can be attained by disposing two biaxial retardationlayers (b3) each having a front retardation of about λ/4 and aretardation in the thickness direction of λ/2 or more. A biaxialretardation layer (b3) with an Nz factor of about 2 or more satisfiesthe above described required condition. A section of the structure andarrangement of layers thereof in this case are as shown in FIGS. 6 and7. In the case, a relationship between the slow axis of a biaxialretardation layer (b3) and the polarization axis of a linearpolarization type reflection polarizer (a2) are as described above andan angle between the axes of biaxial retardation layers (b3) themselvescan be set arbitrarily.

Note that a front retardation of about λ/4 means that the retardation ispreferably on the order of λ/4±40 nm and more preferably on the order ofλ/4±15 nm relative to light with a wavelength of 550 nm.

A similar effect can also be obtained by using one biaxial retardationlayer (b4) having a front retardation of about λ/2 and a retardation inthe thickness direction of λ/2 or more. A biaxial retardation layer (b4)with an Nz factor of about 1.5 or more satisfies the above describedrequired condition. A section of the structure and arrangement of layersthereof in this case are as shown in FIGS. 8 and 9. In the case, arelationship between the axes of the linear polarization type reflectionpolarizers (a2) one above the other and the axis of the biaxialretardation layer (b4) inserted in the middle assumes angles asdesignated and the angles are specially determined.

Note that a front retardation of about λ/2 means that the retardation ispreferably on the order of λ/2±40 nm and more preferably on the order ofλ/2±15 nm relative to light with a wavelength of 550 nm.

As the biaxial retardation layers (b3) and (b4), employed are, to beconcrete, a layer obtained by biaxially stretching a plastic materialhaving birefringence such as polycarbonate, polyethylene terephthalateor the like; and a layer obtained by uniaxially aligning a liquidcrystal material in a plane direction and further aligning the liquidcrystal material in the thickness direction so as to have hybridalignment. A layer obtained by subjecting a liquid crystal material touniaxial homeotropic alignment can be employed, which is formed by meansof a method similar to the method used in film formation of thecholesteric liquid crystal. A necessity arises for use of a nematicliquid crystal material instead of a cholesteric liquid crystalmaterial.

(Arrangement of Diffusing Reflection Plate (F))

A diffusing reflection plate (F) is desirably arranged on the lower sideof a light guide plate (E) as a light source (the other side from anarrangement surface of a liquid cell). A main component of lightreflected by a collimating film is an obliquely incident light componentand the main component of light is specularly reflected and reflectedback in the backlight direction. On this occasion, in a case where areflection plate on the back surface side is high in specularreflection, a reflection angle is retained and cannot be emitted in thefront direction only to end up with light loss. Therefore, a reflectionangle of reflected-back light is not retained to thereby increase ascattering reflection component in the front direction; therefore thearrangement of a diffusing reflection plate (F) is desirable.

(Arrangement of Diffusion Plate (D))

It is also desirable to place a proper diffusion plate (D) between acollimating film in this invention and the backlight light source. Thisis because light impinging obliquely and reflected is scattered in thevicinity of a backlight guide plate and part of the reflected light isscattered in the vertical incidence direction to thereby enhance areutilization of light.

A used diffusion plate (D) can be obtained by means of a method in whicha surface irregularity in depressions and projections is utilized, or inwhich particles with different refractive indexes are embedded in aresin. The diffusion plate (D) either may be inserted between acollimating film and a backlight or may be laminated to a collimatingfilm.

In a case where a liquid crystal cell to which a collimating film islaminated is placed in the near of a backlight, there is a possibilityto cause a Newton ring in a clearance between a film surface and thebacklight, while by placing a diffusion plate (D) having a surfaceirregularity in depressions and projections on the light guide plateside surface of the collimating film in this invention, it can besuppressed to generation of Newton ring. Moreover, a layer serving as asurface irregularity in depressions and projections and a lightdiffusing structure may be formed as a surface itself of a collimatingfilm in this invention.

(Arrangement of View Angle Magnifying film (W))

Magnification of a viewing angle in a liquid crystal display of thisinvention can be achieved by obtaining a uniform and good displaycharacteristic all over the viewing angle through diffusion of light ofgood display characteristic in the vicinity of the front obtained from aliquid crystal displays combined with a collimated backlight.

A viewing angle magnifying layer (W) used here is a diffusion platehaving substantially no backscattering. A diffusion plate can beprovided with a diffusion pressure-sensitive material. An arrangementplace thereof can be used above or below a polarizing plate (PL) on theviewer side of the liquid crystal display. In order to prevent reductionin contrast due to an influence such as bleeding of pixels or a slightlyremaining backscattering, the diffusion plate is desirably provided in alayer at a position closest possible to a cell such as between apolarizing plate (PL) and a liquid crystal cell (LC). In this case, itis desirable to use a film that does not substantially cancelpolarization. A fine particle distribution type diffusion plate ispreferably used, which is disclosed in, for example, the publications ofJP-A No. 2000-347006 and JP-A No. 2000-347007.

In a case where a viewing angle magnifying layer (W) is disposed outsideof a polarizing plate (PL) on the viewer side of a liquid crystal cell(LC), a viewing angle compensating retardation plate may not be usedespecially if a TN liquid crystal cell is used since collimated lightsare transmitted through a liquid crystal cell (LC) and through thepolarizing plate (PL). If an STN liquid crystal cell is used in thecase, it has only to use a retardation film that is well compensatedwith respect to a front characteristic. Since, in this case, a viewingangle magnifying layer (W) has a surface exposed to air, a type having arefractive effect due to a surface profile can also be employed.

On the other hand, in a case where a viewing angle magnifying film (W)is inserted between a polarizing plate (PL) and a liquid crystal cell(LC), light is diffused light at the stage where light is transmittedthrough the polarizing plate (PL). If a TN liquid crystal is used, anecessity arises for compensating a viewing angle characteristic of thepolarizer itself. In this case, it is preferable to insert a retardationplate (C) to compensate a viewing angle characteristic of a polarizingplate (PL) between the polarizing plate (PL) and the viewing anglemagnifying layer (W). If an STN liquid crystal is used, it is preferableto insert a retardation plate (C) to compensate a viewing anglecharacteristic of the polarizing plate (PL) in addition to a frontretardation compensation for the STN liquid crystal.

In a case of a viewing angle magnifying film having a regular structurein the interior thereof such as a microlens array or a hologram film,both conventionally having been available, interference has occurredwith a fine structure such as a microlens array, a prism array, alouver, a micromirror array or the like that is included in a blackmatrix of a liquid crystal display or a collimation system of aconventional backlight to thereby cause a moiré pattern with ease. Sincein a collimating film in this invention, a regular structure is notvisually recognized in a plane thereof and emitted light has noregularity modulation, no necessity arises for consideration of matchingwith a viewing angle magnifying layer (W) or an arrangement sequence.Therefore, a viewing angle magnifying layer (W) has a lot of optionssince no specific limitation is imposed thereon, if neither interferencenor a moiré pattern occurs with a pixel black matrix of a liquid crystaldisplay.

In this invention, as viewing angle magnifying layers (W), preferablyused are a light scattering plate, having no substantial backscatteringand not canceling polarization, which is described in any of thepublications of JP-A Nos. 2000-347006 and 2000-347007 and which has ahaze in the range of 80% to 90%. Any of layers each of which has aregular structure in the interior thereof such as a hologram sheet, amicroprism array, a microlens array or the like can be used, if neitherinterference nor a moiré pattern occurs with a pixel black matrix of aliquid crystal display.

(Lamination of Layers)

Lamination of each of the layers may be realized only by being laminatedon a preceding layer, while it is preferable to laminate the layers withan adhesive agent or a pressure-sensitive adhesive agent from theviewpoint of workability and light utilization efficiency. In that case,it is desirable from the viewpoint of suppressed surface reflection thatan adhesive agent or a pressure-sensitive adhesive agent is transparentand does not have absorption in the visible light region, and haverefractive indexes closest possible to refractive indexes of the layers.Preferably used from the view point are an acrylic pressure-sensitiveadhesive agent and the like. The following methods can be adopted: onemethod in which each of the layers forms monodomain with the help of analignment film separately from the others and sequentially laminated bytransfer the layers onto a light transparent base material; and theother in which each of the layers is sequentially formed directly on apreceding layer while forming an alignment film or the like foralignment in a proper manner.

It is possible to further add particles for adjusting diffusibility,when required, to thereby impart isotropic scatterbility, and toproperly add an ultraviolet absorbent, an antioxidant, and a surfactantfor a purpose to impartation of a leveling property in film formation,in each of the layers and (pressure-sensitive) adhesive layers.

As far as a reflection polarizer (a) and a retardation layer (b) used ina polarization element (A) in this invention satisfy the requiredconditions described above, it is possible to transmit light in thefront direction with less of wavelength dependency but to cut off lightin an oblique direction by reflection. A polarization element (A) inthis invention has a feature that dependency on a characteristic of alight source is less as compared with a conventional technique, forexample a collimation/light condensation system with combination of aninterference filter and a bright-line emission light source, which isdisclosed in the specification of USP No. 2002/36735 A.

(Other Materials)

Note that various other kinds of optical layers are properly employedaccording a common method to thereby, manufacture a liquid crystaldisplay.

Polarizing plates (PL) are disposed on both sides of a liquid crystalcell. The polarizing plates (PL) disposed on both sides of the liquidcrystal cell are arranged so that the polarization axes thereof arealmost perpendicular to each other. The polarizing plate (PL) on theincidence side is arranged so that the polarization axis directionthereof is aligned with the axis direction of a linearly polarized lightobtained by transmission from the light source.

Commonly used is a polarizing plate (PL) having a protective film on oneside or both sides of a polarizer.

A polarizer is not limited especially but various kinds of polarizer maybe used. As a polarizer, for example, a film that is uniaxiallystretched after having dichromatic substances, such as iodine anddichromatic dye, absorbed to hydrophilic high molecular weight polymerfilms, such as polyvinyl alcohol type film, partially formalizedpolyvinyl alcohol type film, and ethylene-vinyl acetate copolymer typepartially saponified film; poly-ene type orientation films, such asdehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride,etc. may be mentioned. In these, a polyvinyl alcohol type film on whichdichromatic materials such as iodine is absorbed and oriented afterstretched is suitably used. Although thickness of polarizer is notespecially limited, the thickness of about 5 to 80 μm is commonlyadopted.

A polarizer that is uniaxially stretched after a polyvinyl alcohol typefilm dyed with iodine is obtained by stretching a polyvinyl alcohol filmby 3 to 7 times the original length, after dipped and dyed in aqueoussolution of iodine. If needed the film may also be dipped in aqueoussolutions, such as boric acid and potassium iodide, which may includezinc sulfate, zinc chloride. Furthermore, before dyeing, the polyvinylalcohol type film may be dipped in water and rinsed if needed. Byrinsing polyvinyl alcohol type film with water, effect of preventingun-uniformity, such as unevenness of dyeing, is expected by makingpolyvinyl alcohol type film swelled in addition that also soils andblocking inhibitors on the polyvinyl alcohol type film surface may bewashed off. Stretching may be applied after dyed with iodine or may beapplied concurrently, or conversely dyeing with iodine may be appliedafter stretching. Stretching is applicable in aqueous solutions, such asboric acid and potassium iodide, and in water bath.

As the transparent protective film prepared on one side or both sides ofthe polarizer, materials is excellent in transparency, mechanicalstrength, heat stability, water shielding property, isotropy, etc. maybe preferably used. As materials of the above-mentioned transparentprotective film, for example, polyester type polymers, such aspolyethylene terephthalate and polyethylenenaphthalate; cellulose typepolymers, such as diacetyl cellulose and triacetyl cellulose; acrylicstype polymer, such as poly methylmethacrylate; styrene type polymers,such as polystyrene and acrylonitrile-styrene copolymer (AS resin);polycarbonate type polymer may be mentioned. Besides, as examples of thepolymer forming a protective film, polyolefin type polymers, such aspolyethylene, polypropylene, polyolefin that has cyclo- type ornorbornene structure, ethylene-propylene copolymer; vinyl chloride typepolymer; amide type polymers, such as nylon and aromatic polyamide;imide type polymers; sulfone type polymers; polyether sulfone typepolymers; polyether-ether ketone type polymers; poly phenylene sulfidetype polymers; vinyl alcohol type polymer; vinylidene chloride typepolymers; vinyl butyral type polymers; allylate type polymers;polyoxymethylene type polymers; epoxy type polymers; or blend polymersof the above-mentioned polymers may be mentioned as a. Films made ofheat curing type or ultraviolet ray curing type resins, such as acrylbased, urethane based, acryl urethane based, epoxy based, and siliconebased, etc. may be mentioned as materials of the above-mentionedtransparent protective film.

Moreover, as is described in Japanese Patent Laid-Open Publication No.2001-343529 (WO 01/37007), polymer films, for example, resincompositions including (A) thermoplastic resins having substitutedand/or non-substituted imido group is in side chain, and (B)thermoplastic resins having substituted and/or non-substituted phenyland nitrile group in side chain may be mentioned. As an illustrativeexample, a film may be mentioned that is made of a resin compositionincluding alternating copolymer comprising iso-butylene and N-methylmaleimide, and acrylonitrile-styrene copolymer. A film comprisingmixture extruded article of resin compositions etc. may be used.

In general, a thickness of the protection film, which can be determinedarbitrarily, is 500 μm or less, preferably 1 through 300 μm, andespecially preferably 5 through 200 μm in viewpoint of strength, workhandling and thin layer

Moreover, it is preferable that the protective film may have as littlecoloring as possible. Accordingly, a protective film having aretardation value in a film thickness direction represented byRth=[(nx+ny)/2−nz]×d of −90 nm through +75 nm (where, nx and nyrepresent principal indices of refraction in a film plane, nz representsrefractive index in a film thickness direction, and d represents a filmthickness) may be preferably used. Thus, coloring (optical coloring) ofpolarizing plate resulting from a protective film may mostly becancelled using a protective film having a retardation value (Rth) of−90 nm through +75 nm in a thickness direction. The retardation value(Rth) in a thickness direction is preferably −80 nm through +60 nm, andespecially preferably −70 nm through +45 nm.

As a protective film, if polarization property and durability are takeninto consideration, cellulose based polymer, such as triacetylcellulose, is preferable, and especially triacetyl cellulose film issuitable. In addition, when the protective films are provided on bothsides of the polarizer, the protective films comprising same polymermaterial may be used on both of a front side and a back side, and theprotective films comprising different polymer materials etc. may beused. Adhesives are used for adhesion processing of the above describedpolarizer and the protective film. As adhesives, isocyanate derivedadhesives, polyvinyl alcohol derived adhesives, gelatin derivedadhesives, vinyl polymers derived latex type, aqueous polyurethane basedadhesives, aqueous polyesters derived adhesives, etc. may be mentioned.

A hard coat layer may be prepared, or antireflection processing,processing aiming at sticking prevention, diffusion or anti glare may beperformed onto the face on which the polarizing film of the abovedescribed transparent protective film has not been adhered.

A hard coat processing is applied for the purpose of protecting thesurface of the polarizing plate from damage, and this hard coat film maybe formed by a method in which, for example, a curable coated film withexcellent hardness, slide property etc. is added on the surface of thetransparent protective film using suitable ultraviolet curable typeresins, such as acrylic type and silicone type resins. Antireflectionprocessing is applied for the purpose of antireflection of outdoordaylight on the surface of a polarizing plate and it may be prepared byforming an antireflection film according to the conventional method etc.Besides, a sticking prevention processing is applied for the purpose ofadherence prevention with adjoining layer.

In addition, an anti glare processing is applied in order to prevent adisadvantage that outdoor daylight reflects on the surface of apolarizing plate to disturb visual recognition of transmitting lightthrough the polarizing plate, and the processing may be applied, forexample, by giving a fine concavo-convex structure to a surface of theprotective film using, for example, a suitable method, such as roughsurfacing treatment method by sandblasting or embossing and a method ofcombining transparent fine particle. As a fine particle combined inorder to form a fine concavo-convex structure on the above-mentionedsurface, transparent fine particles whose average particle size is 0.5to 50 μm, for example, such as inorganic type fine particles that mayhave conductivity comprising silica, alumina, titania, zirconia, tinoxides, indium oxides, cadmium oxides, antimony oxides, etc., andorganic type fine particles comprising cross-linked of non-cross-linkedpolymers may be used. When forming fine concavo-convex structure on thesurface, the amount of fine particle used is usually about 2 to 50weight parts to the transparent resin 100 weight parts that forms thefine concavo-convex structure on the surface, and preferably 5 to 25weight parts. An anti glare layer may serve as a diffusion layer(viewing angle expanding function etc.) for diffusing transmitting lightthrough the polarizing plate and expanding a viewing angle etc.

In addition, the above-mentioned antireflection layer, stickingprevention layer, diffusion layer, anti glare layer, etc. may be builtin the protective film itself, and also they may be prepared as anoptical layer different from the transparent protective film.

A retardation plate is laminated on a polarizing plate as a viewingangle compensating film and used as a wide viewing angle polarizingplate. A viewing angle compensating film is a film for magnifying aviewing angle so as to enable an image to be viewed with relativelysharpness even in a case where a screen image of a liquid crystaldisplay is viewed not in a direction normal to the screen but in aslightly oblique direction relative to the screen.

As such viewing angle compensating retardation plates, there areavailable, in addition thereto, a film having a birefringence obtainedby a biaxially stretching treatment, a stretching treatment in twodirections perpendicular to each other or the like and a biaxiallystretched film such as an inclined alignment film. As inclined alignmentfilm, for example, a film obtained using a method in which a heatshrinking film is adhered to a polymer film, and then the combined filmis heated and stretched or shrinked under a condition of beinginfluenced by a shrinking force, or a film that is oriented in obliquedirection may be mentioned. The viewing angle compensation film issuitably combined for the purpose of prevention of coloring caused bychange of visible angle based on retardation by liquid crystal cell etc.and of expansion of viewing angle with good visibility.

Besides, a compensation plate in which an optical anisotropy layerconsisting of an alignment layer of liquid crystal polymer, especiallyconsisting of an inclined alignment layer of discotic liquid crystalpolymer is supported with triacetyl cellulose film may preferably beused from a viewpoint of attaining a wide viewing angle with goodvisibility.

No specific limitation is, in addition to the above described condition,imposed on optical layers laminated when being actually used and therecan be used one, or two or more optical layers that have an opportunityto be used in formation of a liquid crystal display and others, such asa reflection plate and a transflective plate. Examples thereofespecially include: a reflection type polarizing plate and atransflective type polarizing plate obtained by laminating a reflectionplate and a transflective plate, respectively, on an elliptic polarizingplate or a circular polarizing plate.

A reflective layer is prepared on a polarizing plate to give areflection type polarizing plate, and this type of plate is used for aliquid crystal display in which an incident light from a view side(display side) is reflected to give a display. This type of plate doesnot require built-in light sources, such as a backlight, but has anadvantage that a liquid crystal display may easily be made thinner. Areflection type polarizing plate may be formed using suitable methods,such as a method in which a reflective layer of metal etc. is, ifrequired, attached to one side of a polarizing plate through atransparent protective layer etc.

As an example of a reflection type polarizing plate, a plate may bementioned on which, if required, a reflective layer is formed using amethod of attaching a foil and vapor deposition film of reflectivemetals, such as aluminum, to one side of a matte treated protectivefilm. Moreover, a different type of plate with a fine concavo-convexstructure on the surface obtained by mixing fine particle into theabove-mentioned protective film, on which a reflective layer ofconcavo-convex structure is prepared, may be mentioned. The reflectivelayer that has the above-mentioned fine concavo-convex structurediffuses incident light by random reflection to prevent directivity andglaring appearance, and has an advantage of controlling unevenness oflight and darkness etc. Moreover, the protective film containing thefine particle has an advantage that unevenness of light and darkness maybe controlled more effectively, as a result that an incident light andits reflected light that is transmitted through the film are diffused. Areflective layer with fine concavo-convex structure on the surfaceeffected by a surface fine concavo-convex structure of a protective filmmay be formed by a method of attaching a metal to the surface of atransparent protective layer directly using, for example, suitablemethods of a vacuum evaporation method, such as a vacuum depositionmethod, an ion plating method, and a sputtering method, and a platingmethod etc.

Instead of a method in which a reflection plate is directly given to theprotective film of the above-mentioned polarizing plate, a reflectionplate may also be used as a reflective sheet constituted by preparing areflective layer on the suitable film for the transparent film. Inaddition, since a reflective layer is usually made of metal, it isdesirable that the reflective side is covered with a protective film ora polarizing plate etc. when used, from a viewpoint of preventingdeterioration in reflectance by oxidation, of maintaining an initialreflectance for a long period of time and of avoiding preparation of aprotective layer separately etc.

In addition, a transflective type polarizing plate may be obtained bypreparing the above-mentioned reflective layer as a transflective typereflective layer, such as a half-mirror etc. that reflects and transmitslight. A transflective type polarizing plate is usually prepared in thebackside of a liquid crystal cell and it may form a liquid crystaldisplay of a type in which a picture is displayed by an incident lightreflected from a view side (display side) when used in a comparativelywell-lighted atmosphere. And this unit displays a picture, in acomparatively dark atmosphere, using embedded type light sources, suchas a back light built in backside of a transflective type polarizingplate. That is, the transflective type polarizing plate is useful toobtain of a liquid crystal display of the type that saves energy oflight sources, such as a back light, in a well-lighted atmosphere, andcan be used with a built-in light source if needed in a comparativelydark atmosphere etc.

Moreover, the polarizing plate may consist of multi-layered film oflaminated layers of a polarizing plate and two of more of optical layersas the above-mentioned separated type polarizing plate. Therefore, apolarizing plate may be a reflection type elliptically polarizing plateor a transflective type elliptically polarizing plate, etc. in which theabove-mentioned reflection type polarizing plate or a transflective typepolarizing plate is combined with above described retardation platerespectively.

While a polarizing plate and a retardation plate described above can beformed by sequentially laminating layers one at a time in amanufacturing process for a liquid crystal display, an optical film suchas an elliptic polarizing plate or the like obtained by lamination inadvance has an advantage of being excellent in quality stability,workability in lamination and others and enabling a productionefficiency of a liquid crystal display to be improved.

A pressure-sensitive adhesive layer or an adhesive layer can also beprovided in an optical element of this invention. A pressure-sensitivelayer can be used for adherence to a liquid crystal cell and inaddition, is used in lamination of optical layers. In adherence of theoptical film, the optical axis thereof can be set at a properarrangement angle in adaptation for a retardation characteristic as atarget.

In the polarizing plate mentioned above and the optical film in which atleast one layer of the polarizing plate is laminated, an adhesive layermay also be prepared for adhesion with other members, such as a liquidcrystal cell etc.

As the pressure sensitive adhesive agent or the adhesive agent is notespecially limited. For example, polymers such as acrylic type polymers;silicone type polymers; polyesters, polyurethanes, polyamides, polyvinylethers, vinyl acetate/vinyl chloride copolymers, modified polyolefines,epoxy type; and rubber type such as fluorine type, natural rubber,synthetic rubber may be suitably selected as a base polymer. Especially,the one which is excellent in optical transparency, showing adhesioncharacteristics with moderate wettability, cohesiveness and adhesiveproperty and has outstanding weather resistance, heat resistance, etc.may be preferably used.

The pressure sensitive adhesive agent or the adhesive agent adhesive maycontain cross-linking agent according to a base polymer. And theadhesive agent adhesive may contain additives, for example, such asnatural or synthetic resins, adhesive resins, glass fibers, glass beads,metal powder, fillers comprising other inorganic powder etc., pigments,colorants and antioxidants. Moreover, it may be an adhesive layer thatcontains fine particle and shows optical diffusion nature.

An adhesive agent and a pressure-sensitive adhesive agent each areusually used as an adhesive agent solution of a base polymer or acomposition thereof dissolved or dispersed in a solvent at a solidmatter concentration of the order in the range of from 10 to 50 wt %. Anorganic solvent can be properly selected from the group consisting oftoluene, ethyl acetate and others; water; or others, so as to be adaptedfor a kind of an adhesive agent for use.

An adhesive layer and pressure-sensitive adhesive layer may also beprepared on one side or both sides of a polarizing plate or an opticalfilm as a layer in which pressure sensitive adhesives with differentcomposition or different kind etc. are laminated together. Moreover,when adhesive layers are prepared on both sides, adhesive layers thathave different compositions, different kinds or thickness, etc. may alsobe used on front side and backside of a polarizing plate or an opticalfilm. Thickness of an adhesive layer may be suitably determineddepending on a purpose of usage or adhesive strength, etc., andgenerally is 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10to 100 μm.

A temporary separator is attached to an exposed side of an adhesivelayer to prevent contamination etc., until it is practically used.Thereby, it can be prevented that foreign matter contacts adhesive layerin usual handling. As a separator, without taking the above-mentionedthickness conditions into consideration, for example, suitableconventional sheet materials that is coated, if necessary, with releaseagents, such as silicone type, long chain alkyl type, fluorine typerelease agents, and molybdenum sulfide may be used. As a suitable sheetmaterial, plastics films, rubber sheets, papers, cloths, no wovenfabrics, nets, foamed sheets and metallic foils or laminated sheetsthereof may be used.

In addition, in the present invention, ultraviolet absorbing propertymay be given to the above-mentioned each layer, such as a polarizer fora polarizing plate, a transparent protective film and an optical filmetc. and an adhesive layer, using a method of adding UV absorbents, suchas salicylic acid ester type compounds, benzophenol type compounds,benzotriazol type compounds, cyano acrylate type compounds, and nickelcomplex salt type compounds.

EXAMPLES

Description will be given of the present invention showing examples,while this invention is not restricted to the examples shown below.

Note that as to a front retardation, a direction in which an in-planerefractive index is maximized is referred to as X axis, a directionperpendicular to the X axis as Y axis and the thickness direction of afilm as Z axis, and refractive indexes in the axis directions as nx, nyand nz, respectively; and from the refractive indexes nx, ny and nz at550 nm measured with an automatic birefringence measuring instrument(manufactured by Oji Sceientific Instruments with a trade name ofautomatic birefringence meter KOBRA21ADH) and a thickness d (nm) of aretardation layer, a front retardation: (nx−ny)×d, and a retardation inthe thickness direction: (nx−nz)×d were calculated. Retardation whenmeasured in an inclined state can be measured with the automaticbirefringence measuring instrument. Inclination retardation is expressedby a value of (nx−ny)×d when being inclined.

Nz factor is defined with a formula: Nz=(nx−nz)/(nx−ny).

Note that a reflectance spectrum was measured with a spectrophotometer(Instant multiphotometry system MCPD-2000, manufactured by OtsukaElectronics Co., Ltd.) and a reflection wavelength band is defined as awavelength band having a half value of the maximum reflectance.

Other measuring instruments used in experiments are as follows:

Measurement on Haze was conducted with Haze meter HM150 manufactured byMurakami Color Research Laboratory.

Transmission/reflection spectral characteristics were measured withSpectrophotometer U4100 manufactured by Hitachi, Ltd.

A characteristic of a polarizing plate was measured with DOT3manufactured by Murakami Color Research Laboratory.

Measurement on brightness was conducted with a brightness meter BM7manufactured by TOPCON CORPORATION.

Illumination with ultraviolet was conducted with UVC321AMI manufacturedby USHIO INC.

Example 1

(Preparation of Circular Polarization Type Reflection Polarizer (a1))

The circular polarization type reflection polarizer (a1) was preparedwith a polymerizable nematic liquid crystal monomer and a chiral agentsold on the market. A used cholesteric liquid crystal was obtained froma mixture of a polymerizable mesogen compound and a polymerizable chiralagent, wherein LC242 manufactured by BASF Japan Ltd. was used as thepolymerizable mesogen compound, and LC756 manufactured by BASF JapanLtd. was used as the polymerizable chiral agent.

The polymerizable mesogen compound and the polymerizable chiral agentwere mixed in a mixing ratio of 5 to 95 in weight ratio so that acentral wavelength in selective reflection of an obtainable cholestericliquid crystal was about 550 nm. The obtained cholesteric liquid crystalhad a central wavelength in selective reflection was 545 nm and aselective reflection wavelength bandwidth was about 60 nm.

A detailed method was as follows: The polmerizable chiral agent and thepolymerizable mesogen compound were dissolved (at 20 wt %) incyclopentane and a reaction initiator (IRGACURE 907 manufactured by CibaSpecialty Chemicals. at 1 wt % relative to the mixture) was added to themixture to prepare a solution. An alignment substrate in use wasobtained by alignment treating a polyethylene terephthalate film:LUMIRROR (a thickness of 75 μm) manufactured by TORAY INDUSTRIES INC.with a rubbing cloth.

The solution was coated to a thickness of 5 μm as measured in a drystate with wire bar, the wet coat was dried at 90° C. for 2 min,thereafter heated temporarily to an isotropic transition temperature130° C. and thereafter gradually cooled. A uniform alignment state wasretained and the coat was cured by illumination with ultraviolet (at 10mW/cm² for 1 min) in an environment at 80° C. to thereby obtain thecircular polarization type reflection polarizer (a1). The obtainedcircular polarization type reflection polarizer (a1) was transferredonto a glass plate using a light transparent acrylic pressure-sensitiveadhesive agent (manufactured by NITTO DENKO CORPORATION with No. 7 to athickness of 25 μm). A selective reflection wavelength band of theobtained circular polarization type reflection polarizer (a1) rangedfrom about 520 to about 580 nm.

(Preparation of Negative C Plate)

Then, a retardation layer (b1: negative C plate) having a frontretardation of almost 0 and a retardation of a value at an obliquedirection was prepared with a polymerized liquid crystal. LC242manufactured by BASF Japan Ltd. was used as a polymerizable mesogencompound and LC756 manufactured by BASF Japan Ltd. was used as apolymerizable chiral agent.

The polymerizable mesogen compound and the polymerizable chiral agentwere mixed in a mixing ratio of 11 to 88 in weight ratio so that acentral wavelength in selective reflection of an obtainable cholestericliquid crystal was about 350 nm. The obtained cholesteric liquid crystalhad a central wavelength in selective reflection was 350 nm.

A detailed method was as follows. The polymerizable chiral agent and thepolymerizable mesogen compound were dissolved (at 30 wt %) incyclopentane and a reaction initiator (IRGACURE 907 manufactured by CibaSpecialty Chemicals. at 1 wt % relative to the mixture) was added to themixture to prepare a solution. An alignment substrate in use wasobtained by alignment treating a polyethylene terephthalate film:LUMIRROR (a thickness of 75 μm) manufactured by TORAY INDUSTRIES INC.with a rubbing cloth.

The solution was coated to a thickness of 7 μm as measured in a drystate with wire bar, the wet coat was dried at 90° C. for 2 min,thereafter heated temporarily to an isotropic transition temperature130° C. and thereafter gradually cooled. A uniform alignment state wasretained and the coat was cured by illumination with ultraviolet (at 10mW/cm² for 1 min) in an environment at 80° C. to thereby obtain thenegative C plate (b1). The negative C plate (b1) was measured on aretardation thereof with the result that a retardation in the frontdirection was 2 nm and a retardation when being inclined by 30° wasabout 190 nm (>λ/8) for light with a wavelength of 550 nm.

(Preparation of Polarization Element (A) and a Backlight System UsingSame)

The negative C plate (b1) was adhered to the top of the circularpolarization type reflection polarizer (a1) obtained in the abovedescribed process with a light transparent acrylic pressure-sensitiveadhesive agent (manufactured by NITTO DENKO CORPORATION with No. 7 to athickness of 25 μm) and thereafter, the substrate was separated andremoved off. The circular polarization type reflection polarizer (a1)was transferred and laminated thereon to thereby obtain the polarizationelement (A) of this invention. Since this sample does not cover theentire visible light region because of a narrow band thereof, acollimation effect was confirmed with a monochromatic light source.

A green diffusion light source having a bright-line at 544 nm wasprovided to the obtained polarization element (A). As to the lightsource, GO type manufactured by Elevam Corp. as a cold cathodefluorescent lamp was placed in a dot printing side light type backlightunit (E) manufactured by Chatani Kogyo K.K. and a light diffusing plate(D manufactured by Kimoto Co., Ltd. with a haze of 90% or more) wasinserted between the light source and the polarization element (A),which was used as a diffusion light source. A diffusing reflection plate(F) obtained by evaporating with silver on a matt PET was disposed onthe lower surface of the backlight.

It was confirmed that the polarization element (A) placed on thediffusion light source emits lights in the normal direction, whiletransmitted light started sudden decrease at an angle of the order of20° in an oblique direction, decreased by half at 30° in an obliquedirection and emitted light came to almost nothing at about 45° in anoblique direction.

(Manufacture of Viewing Angle Magnification Liquid Crystal Display)

Then, a TN liquid crystal cell (LC) sold on the market was provided to amonochromatic light source backlight using the polarization element (A).A TFT liquid crystal cell (with 10.4-inch diagonal screen) manufacturedby TOSHIBA CORP. without a retardation film for viewing angle correctionwas used as the TN liquid crystal. The polarizing plates (PL) one abovethe other were used adhering SEG1425DU manufactured by NITTO DENKOCORPORATION as replacement thereto.

A λ/4 plate (an NRF film manufactured by NITTO DENKO CORPORATION with afront retardation of 140 nm) as a retardation layer (B) was disposed onthe previously prepared light condensing backlight. The polarizing plate(PL) on the lower surface of the liquid cell was arranged so that thepolarization axis direction thereof forms an angle of 45° relative tothe slow axis of the retardation layer (B), and the back surface of theliquid crystal cell (LC), the polarizing plate (PL), the λ/4 plate (B)and the polarization element (A) were adhered to one another with alight transparent acrylic pressure-sensitive adhesive agent(manufactured by NITTO DENKO CORPORATION with No. 7 to a thickness of 25μm) in arrangement in which a front transmitted light amount wasmaximized.

Moreover, a light diffusion pressure-sensitive adhesive layer with aHaze of 92% as a viewing angle magnifying layer (W) was prepared bydispersing true spherical silica particles (with a particle size of 4μm, a mixing content of 30 wt % and a refractive index of 1.44) in alight transparent acrylic pressure-sensitive adhesive agent (No. 7 witha refractive index of 1.47 manufactured by NITTO DENKO CORPORATION). Athickness thereof was about 30 μm. The light diffusionpressure-sensitive adhesive layer was adhered between the polarizingplate (PL) on the front surface side of the liquid crystal display andthe liquid crystal cell (LC).

The obtained viewing angle magnification liquid crystal display is asshown in FIG. 11. The viewing angle magnification liquid crystal displaydoes not cause gray scale inversion within ±60° of an inclination anglerelative to the normal direction and maintains a good displaycharacteristic in a viewing angle characteristic in a gray scalerepresentation. Since the viewing angle magnifying layer (W) wasinserted between the polarizing plate (PL) and the liquid crystal cell(LC), light transmitted in the direction normal to the liquid crystalcell (LC) is not influenced of the viewing angle characteristic of theliquid crystal, while being some influenced of the viewing anglecharacteristic of the polarizing plate (PL). A characteristic of theliquid crystal display of this invention was improved as compared with aconventional liquid crystal display without adopting a combination ofthe collimating light source and the viewing angle magnifying layer (W)in this invention.

Example 2

(Preparation of Positive C Plate)

A retardation layer (b1 as a positive C plate) having a frontretardation of O and a retardation in an oblique direction of a valuewas prepared with a polymerized liquid crystal. Used as a polymerizableliquid crystal compound was a polymerizable nematic liquid crystalmonomer A expressed by the following chemical formula 1:

A detailed method was as follows. The polymerizable nematic liquidcrystal monomer A was dissolved in cyclopentane (at 30 wt %) and areaction initiator (IRGACURE 907 manufactured by Ciba SpecialtyChemicals. at 1 wt % relative to the monomer A) was added to the monomerA to prepare a solution. An vertical alignment film in use was formed bycoating a cyclohexane solution (at 0.1 wt %) of a release agent(octadecyltrimethoxysilane) on a polyethylene terephthalate film:LUMIRROR (a thickness of 75 μm) manufactured by TORAY INDUSTRIES INC. todry the coat.

The polymerizable nematic liquid crystal monomer A solution was coatedwith a wire bar to a thickness of 2.5 μm as measured in a dry state, thewet coat was dried at 90° C. for 2 min, thereafter heated temporarily toan isotropic transition temperature of 130° C. and thereafter graduallycooled. A uniform alignment state was retained and the coat was cured byillumination with ultraviolet (at 10 mW/cm² for 1 min) in an environmentat 80° C. to thereby obtain the positive C plate (b1). The positive Cplate (b1) was measured on a retardation thereof with the result that aretardation in the front direction was 0 nm and a retardation when beinginclined by 30° was about 200 nm (>λ/8) for light with a wavelength of550 nm.

(Preparation of Polarization Element (A))

The polarizing element A was obtained in a procedure in conformity withExample 1 with the exception that in Example 1, the positive C plate(b1) was used instead of the negative C plate (b1).

(Manufacture of Viewing Angle Magnification Liquid Crystal Display)

The viewing angle magnifying system was assembled using the obtainedpolarization element (A), the liquid crystal display and the lightsource same as in Example 1. A diffusion pressure-sensitive adhesivelayer, which is a viewing angle magnifying layer (W), was adhered on thepolarizing plate (PL) as the upper plate of the liquid crystal displayand an anti-glare treated triacetyl cellulose film (AG, a 80 μm TAC filmwith AGS1 manufactured by NITTO DENKO CORPORATION) was adheredthereonto. The obtained viewing angle magnification liquid crystaldisplay is as shown in FIG. 12. A characteristic was almost of aperformance equal to that of Example 1. Since in Example 2, the viewingangle magnifying layer (W) was disposed on the polarizing plate (PL), aninfluence of a viewing angle characteristic of the polarizing plate (PL)was not exerted more as compared with Example 1, while backscattering ofexternal light (incident light, such as solar light or indoorillumination) occurred, which reduced contrast slightly. A viewing anglecharacteristic was, however, more excellent than in a conventionalliquid crystal display.

Example 3

(Preparation of Linear Polarization Type Reflection Polarizer (a2))

A multilayer film with 20 layers was obtained by alternately controllingthicknesses of thin films with a feed block method so that polyethylenenaphthalate (PEN)/naphthalene dicarboxylate-terephthalate copolyester(co-PEN) were alternately laminated. The multilayer film was uniaxiallystretched. A stretching temperature was about 140° C. and a stretchratio was about threefold in the TD direction. A thickness of each ofthin layers in the obtained stretched film was roughly on the order of0.1 μm. Five stretched films of the obtained 20 layer laminate filmswere further laminated into a five composite layer laminate including100 layers in total, thereby obtaining the linear polarization typereflection polarizer (a2). The linear polarization type reflectionpolarizer (a2) had a reflection function exerted on linearly polarizedlight in a wavelength band of 500 nm or more and 600 nm or less.

(Preparation of Polarization Element (A))

Disposed as the retardation layer (b2) on both sides of the negative Cplate (b1) obtained in Example 1 were λ/4 plates made of a uniaxiallystretched polycarbonate film (a NRF film having a front retardation of135 nm, manufactured by NITTO DENKO CORPORATION). The linearpolarization type reflection polarizer (a2) were arranged outside of theλ/4 plates so that arrangement of the axes of FIG. 5 was established tothereby obtain the polarization element (A). That is, arrangement wasconducted in the following order in a case where the transmission axisof a linear polarization type reflection polarizer (a2) obtained in theprocess described above on the incidence side was set at 0°: the linearpolarization type reflection polarizer (a2), a λ/4 plate (b2) with theaxis set at 45°, a C plate (b1) having no axis direction, a λ/4 plate(b2) with the axis set at −45° and a linear polarization type reflectionpolarizer (a2) obtained in the process described above on the emissionside with the transmission axis set at 90°. The layers were laminatedwith a light transparent acrylic pressure-sensitive adhesive agent(manufactured by NITTO DENKO CORPORATION with No. 7 to a thickness of 25μm). The substrate of the negative C plate (b1) was removed when beingused, similar to Example 1.

(Manufacture of Viewing Angle Magnification Liquid Crystal Display)

The viewing angle magnifying system was assembled using the obtainedpolarization element (A), the liquid crystal display and the lightsource same as in Example 1. A polarizing viewing angle compensatingretardation plate (a biaxially stretched retardation plate made of a 80μm TAC film, manufactured by Fuji Photo Film Co., Ltd.), as aretardation layer (C), was inserted between a polarizing plate (PL) anda viewing angle magnifying layer (W). This is because since lighttransmitted through a liquid cell (LC) in a direction nearly normalthereto is diffused in the viewing angle magnifying layer (W) andthereafter impinges on the polarizing plate (PL), a viewing anglecharacteristic of the polarizing plate (PL) is prevented from beingrevealed, wherein a viewing angle characteristic of the liquid crystalcell (LC) is not revealed. Note that no λ/4 plate (B) was insertedbetween the polarizing plate (PL) and the polarization element (A).

The obtained viewing angle magnification liquid crystal display is asshown in FIG. 13. A characteristic thereof was almost of a performanceequal to that of Example 1 with an improved characteristic of thepolarizing plate itself in a viewing angle deficient region in the axisdirection thereof (in a direction of ±45° obliquely inclined when viewedfrom the front of the screen).

Example 4

(Preparation of Polarization Element (A))

A retardation film (with a front retardation of 270 m and a Nz factor of1.5) obtained by biaxially stretching a polycarbonate film, as aretardation layer (b4), was adhered between two linear polarization typereflection polarizers (a2), obtained in Example 3, with arrangement ofthe respective transmission axes thereof perpendicular to each other inconformity to FIG. 9 to thereby prepare the polariziation element (A).The retardation film was prepared by biaxially stretching an unstretchedpolycarbonate film manufactured by Kaneka Corp. with a biaxialstretching machine. A light transparent acrylic pressure-sensitiveadhesive agent (manufactured by NITTO DENKO CORPORATION with No. 7 to athickness of 25 μm) was employed in adherence of layers therebetween.

(Manufacture of Viewing Angle Magnification Liquid Crystal Display)

A backlight system was manufactured using the obtained polarizationelement (A) in similar way to that in Example 1.

Then, a color STN liquid crystal (with 10.4 in), as a liquid crystalcell (LC), was disposed on a monochromatic light source backlight usingthe polarization element (A). Polarizing plates (PL) one above the otherwere used adhering to SEG1425DU manufactured by NITTO DENKO CORPORATIONas replacement thereto. An STN compensation retardation plate (an NRFfilm, made of a polycarbonate, manufactured by NITTO DENKO CORPORATIONwith a front retardation of 430 nm and a thickness of 50 μm using apressure-sensitive adhesive agent layer to a thickness of 25 μm thereon)as a retardation layer (C) was inserted between the liquid crystal cell(LC) and the polarizing plate (PL). A microlens array sheet with asurface profile as a viewing angle magnifying layer (W) (correspondingto a Haze of 90% with a lens pitch of about 20 μm) was disposed on thepolarizing plate (PL) on the front surface side thereof. The layers wereadhered to one another with a light transparent acrylicpressure-sensitive adhesive agent (manufactured by NITTO DENKOCORPORATION with No. 7 to a thickness of 25 μm).

The obtained viewing angle magnification liquid crystal display is asshown in FIG. 14. The viewing angle magnification liquid crystal displayhas a front maximum contrast of the liquid crystal display as a base aslow as a value of the order of about 20, but without a gray scaleinversion, which is similar to Example 1, and a practical range ofviewing angles was wide.

Example 5

(Preparation of Circular Polarization Type Reflection Polarizer (a1))

A coating liquid containing cholesteric liquid crystal polymers for usein four layers with respective different selective reflection centralwavelengths and a solvent was coated on a rubbing treated surface of atriacetyl cellulose film subjected to a rubbing treatment after apolyimide alignment film was provided in advance to thereby obtain thebroad band circular polarization type reflection polarizer (a1). Theused liquid crystal material was prepared based on the specification ofEP No. 0834754 A to obtain four kinds of cholesteric liquid crystalpolymers with respective selective reflection central wavelengths of 460nm, 510 nm, 580 nm and 660 nm.

A cholesteric liquid crystal polymer was prepared by polymerizing apolymerizable nematic liquid crystal monomer A expressed by thefollowing chemical formula 2:

and a polymerizable chiral agent B expressed by the following chemicalformula 3:

in a liquid crystal mixture with each of proportions (in weight ratios)shown in the following Table 1. Each of the liquid crystal mixtures wasdissolved in a tetrahydrofuran to obtain a 33 wt % solution, thereafternitrogen purge was conducted in an environment at 60° C. and then areaction initiator (azobisisobutylnitrile at 0.5 wt % relative to themixture) was added to the mixture to thereby cause polymerization. Anobtained polymerized material was reprecipitation-separated with diethylether for purification. Selective reflection wavelength bands are shownin Table 1.

TABLE 1 Selective reflection (Mixing ratio) central wavelength monomerA/chiral Selective reflection (nm) agent B wavelength band (nm) 460 nm 9.2/1 430 to 490 nm 510 nm 10.7/1 480 to 550 nm 580 nm 12.8/1 540 to620 nm 660 nm 14.9/1 620 to 710 nm

Each of the cholesteric liquid crystal polymers were dissolved inmethylene chloride to prepare a 10 wt % solution. The solution wascoated on an alignment base material with a wire bar to a thickness ofabout 1.5 μm when measured in a dry state. Used as the alignment basematerial was a triacetyl cellulose film with a thickness of 80 μm(manufactured by Fuji Photo Film Co., Ltd. with a trade name of TD-TAC)and a polyimide layer was coated on a surface thereof to a thickness ofabout 0.1 μm, followed by a rubbing treatment with a rayon rubbingcloth. After the coating, the wet coat was dried at 140° C. for 15 min.After the heat treatment ended, the liquid crystal was cooled to roomtemperature and fixed at the temperature to obtain a thin film.

Liquid crystal thin films in colors were prepared using the respectivecholesteric liquid crystal polymers subjecting to a process similar tothat as described above and thereafter, adhered to one another with atransparent isocyanate adhesive agent AD244 (manufactured by TokushikiCo., Ltd.). The liquid crystal thin films in R and G colors were adheredto each other and then a triacetyl cellulose substrate on the G side wasseparated off. In a similar way, after the liquid crystal thin films inB and G colors were adhered to each other and then a triacetyl cellulosesubstrate on the R side was separated off. By doing so, there wasobtained a cholesteric liquid crystal composite layer with a thicknessof about 10 μm in a structure in which the four liquid crystal layerswere laminated sequentially staring at the shorter wavelength side. Thecircular polarization type reflection polarizer (a1) made of theobtained cholesteric liquid crystal composite layer had a selectivereflection function in the range of from 430 nm to 710 nm.

(Preparation of Polariziation Element (A) and Backlight System UsingSame)

The obtained circular polarization type reflection polarizers (a1) wereadhered on both sides of the negative C plate (b1) prepared in Example 1with a light transparent acrylic pressure-sensitive adhesive agent(manufactured by NITTO DENKO CORPORATION with No. 7 to a thickness of 25μm) to thereby obtain the polarization element (A). The circularpolarization type reflection polarizers (a1) one above the other in usewere of the same rotational sense of circular polarization.

The obtained polarization element (A) was disposed on a direct-undertype backlight (D) manufactured by Tama Denki kogyo K.K using a coldcathode fluorescent lamp with bright-lines at three wavelengths (of 435nm, 545 nm and 610 nm). In this case as well, while light was emitted inthe normal direction, transmitted light was suddenly reduced at anoblique angle of 20° or more, decreases by half at about 30° and wasreduced at about 45° to as low as 10% relative to a front brightness.Since the polarization element (A) was adapted for all the visible lightregion, light in all the visible light region was transmitted only inthe front direction, while functioning as a light condensing elementthrough which no light is transmitted in an oblique direction.

(Manufacture of Viewing Angle Magnification Liquid Crystal Display)

The viewing angle magnification liquid crystal display was obtained bysuperimposing a laminate equal to that of the liquid crystal cell (LC)and the viewing angle magnifying layer (W) same as in Example 2 usingthe obtained backlight system. The obtained viewing angle magnificationliquid crystal display is as shown in FIG. 15.

Example 6

(Preparation of Polarization Element (A) and Backlight System UsingSame)

Used as a linear polarization type reflection polarizer (a2) was DBEFmanufactured by 3M Corp. Retardation layers obtained by biaxiallystretching a polycarbonate film (having a front retardation of 140 nmand an Nz factor of 2), as retardation layers (b3), were adhered to thelinear polarization type reflection polarizer (a2) in a way inconformity with FIGS. 6 and 7 to thereby prepare the polarizationelement (A). The retardation film was prepared by stretching andaligning an unstretched polycarbonate film manufactured by Kaneka Corp.with a biaxial stretching machine. The layers were laminated with alight transparent acrylic pressure-sensitive adhesive agent(manufactured by NITTO DENKO CORPORATION with No. 7 to a thickness of 25μm).

A light diffusing plate (D, manufactured by Kimoto Co., Ltd. with a Hazeof about 90%) was disposed on a side light type backlight (E,manufactured by Stanley electric Co., Ltd.) using a cold cathodefluorescent lamp with bright-lines at three wavelengths (of 435 nm, 545nm and 610 nm) as a light source unit and a polarization element (A) wasdisposed thereon. A diffusing reflection plate (F) obtained byevaporating silver on a matt PET was disposed on the lower surface ofthe backlight.

(Manufacture of Viewing Angle Magnification Liquid Crystal Display)

The viewing angle magnification liquid crystal display shown in FIG. 16was manufactured using the obtained backlight system. Used as a liquidcrystal cell (LC) was a color TFT liquid crystal (10.4 in) manufacturedby TOSHIBA CORP. Used as a viewing angle magnifying layer (W) was amicrolens array sheet with a surface profile. Used as a polarizing plate(PL) was SEG1425DU manufactured by NITTO DENKO CORPORATION

The microlens array sheet corresponds to a Haze of 90. A lens pitch wasabout 20 μm and prepared by transfer formation from a brass made metaldie cut product. A base material film was a clear TAC film with 50 μmmanufactured by Fuji Photo Film Co., Ltd. A form transferring resin wasan ultraviolet polymerizable epoxy resin (manufactured by ASAHI DENKACO., LTD. with a trade name of KR410) and after a metal die wasrelease-treated with a silicone resin, the epoxy resin was dropwiseapplied. The epoxy resin was uniformly spread all the surface with aglass rod and then a base material film was adhered thereto and a formobtained by ultraviolet polymerization (at 10 mW for 30 sec) wastransferred on the film. The form transferred film was adhered to thesurface of the polarizing plate (PL) on the upper side of FIG. 16 withthe base material film placed on the polarizing plate (PL) side and theform transferred surface with irregularity of depressions andprojections exposed to the air. The obtained viewing angle magnificationliquid crystal display had no gray scale inversion observed in the rangewithin ±60° from the front.

Though in the system, interference occurs between the viewing anglemagnifying microlens array and a black matrix of the liquid crystaldisplay to produce a moiré, the moiré can be alleviated by inclining anadherence angle of the microlens array by 45°. No interference occurred,in this case, with the polarization element including the reflectionpolarizer.

Example 7

(Preparation of Polarization Element (A))

DBEF manufactured by 3M Corp. were employed as linear polarization typereflection polarizers (a2). Disposed on both sides of the negative Cplate were (b1) the broad band λ/4 retardation plates obtained bylaminating two uniaxially stretched films made of a polycarbonate withrespective different axes as retardation layers (b2) (a laminateincluding an NRF film manufactured by NITTO DENKO CORPORATION with afront retardation of 140 nm and an NRZ film manufactured by NITTO DENKOCORPORATION with a front retardation of 270 nm and an Nz factor of 0.5).A relationship between axes of the broad band λ/4 retardation plates(b2) is shown in FIG. 17. This is because since the linear polarizationtype reflection polarizers (a2) are of a broad band to cover the entirevisible light region, wavelength characteristics of light condensationand collimation are matched with each other and a difference inreflectance according to a wavelength of reflected light from incidentlight in an oblique direction is suppressed. With such a constructionadopted, when emitted light is reduced in an oblique direction, adifference in light reduction percentage according to a color isreduced, thereby enabling a change in tone to be smaller and lights tobe confined.

The linear polarization type reflection polarizers (a2) were disposed onthe outsides of the broad band λ/4 retardation plates so as to assumearrangement of the axes of FIG. 5 to thereby obtain the polarizationelement (A). That is, arrangement was conducted in the following orderin a case where the transmission axis of a linear polarization typereflection polarizer (a2) on the incidence side was set at 0°, thelinear polarization type reflection polarizer (a2), a λ/4 plate (b2)with the axis set at 45°, a C plate (b1) having no axis direction, a λ/4plate (b2) with the axis set at −45° and a linear polarization typereflection polarizer (a2) on the emission side with the transmissionaxis set at 90°. The layers were laminated with a light transparentacrylic pressure-sensitive adhesive agent (manufactured by NITTO DENKOCORPORATION with No. 7 to a thickness of 25 μm). The base material ofthe negative C plate (b1) was removed when being used, which is similarto Example 1.

(Manufacture of Viewing Angle Magnification Liquid Crystal Display)

A viewing angle magnifying system was assembled, similar to that inExample 1, using the obtained polarization element (A). The obtainedviewing angle magnification liquid crystal display is as shown in FIG.18. A hologram diffusion plate, however, was disposed as a viewing anglemagnifying layer (W). Adopted as a backlight was a side light typebacklight (E) manufactured by Stanley Electric Co., Ltd. using a coldcathode fluorescent lamp of a three wavelength type (adapted for 435 nm,545 nm and 610 nm). A diffusion plate (with a Haze of about 90) wasemployed in combination. A TFT liquid crystal cell (11.3 in)manufactured by Sharp Corp. was employed as a liquid crystal cell (LC).

A characteristic thereof was almost of a performance equal to that ofExample 1 with an improved characteristic of the polarizing plate itselfin a viewing angle deficient region in the axis direction thereof (in adirection of ±45° obliquely inclined when viewed from the front of thescreen).

Comparative Example 1

A polarization element (A) including reflection polarizers (a) andretardation plates (b) was removed each of the viewing anglemagnification liquid crystal displays of Examples 1 to 7. While in anyliquid crystal display, a viewing angle characteristic was made uniformby a diffusion effect of the viewing angle magnifying layer (W),uniformity was realized including light in a region where a gray scaleis inverted; therefore, a brightness in black display was improved tothereby reduce a contrast.

Even if uniformity is realized in the regions outside the range ofinclination angles within ±45° from the normal direction, which regionis where a gray scale is inverted, only an averaged image in which agray scale is inverted is obtained. Therefore, no effect of a viewingangle magnifying layer (W) was observed and a gray scale was inverted,thereby having recognized an unnatural change in darkness and brightnesspattern in gray scale representation.

Comparative Example 2

In Example 6, a light control film manufactured by 3M Corp. was employedinstead of the polarization element (A) to obtain collimated lightsource. Interference occurs, however, between a microlens array and ablack matrix of pixels of the liquid crystal display and a moiré wasvisually recognized. Therefore, while reduction in the pattern was triedby rotating the microlens array, the rotation caused a moiré between themicrolens array and a pitch in the light control roll film only to failin erasure of both patterns.

Comparative Example 3

A polarization element was prepared with a combination similar to thatin Example 3 with the exception that an iodine containing absorptiondichroic polarizer sold on the market (manufactured by NITTO DENKOCORPORATION with a trade name of NPF-EG1425DU) was employed instead ofthe linear polarization type reflection polarizer (a2). A viewing anglemagnification liquid crystal display similar to that in Example 1 wasmanufactured using the polarization element. While obtained were atransmission characteristic in the front direction and an effect ofrestricting a viewing angle caused by an absorption characteristic in anoblique direction, an absorption loss is great and a brightness of thefront is not improved, thereby obtaining only an extremely dark display.

INDUSTRIAL APPLICABILITY

A viewing angle magnification liquid crystal display of the presentinvention is of a thin type and capable of realizing a wide viewingangle.

1. A viewing angle magnification liquid crystal display comprising atleast: a backlight system containing a polarization element (A) whereinsaid polarization element (A) comprises a retardation layer (b) and areflection polarizer (a), wherein said reflection polarization (a)comprises at least two layers and said retardation layer (b) is disposedbetween said at least two layers, and said reflection polarizer (a) hasrespective selective reflection wavelength bands of polarized lightsuperimposed on each other to conduct collimation for a diffusion lightsource; a liquid crystal cell transmitting collimated lights; polarizingplates disposed on both sides of the liquid crystal cell; and a viewingangle magnifying layer disposed on the viewer side of the liquid crystalcell to diffuse transmitted light, wherein the reflection polarizer (a)is a circular polarization type reflection polarizer (a1) transmittingcircularly polarized light but selectively reflecting reverse circularlypolarized light, and the retardation layer (b) comprises a layer (b1)having a front retardation of almost zero and a retardation of λ/8 ormore relative to incident light incoming at a direction inclined fromthe normal direction by 30° or more.
 2. The viewing angle magnificationliquid crystal display according to claim 1, wherein the selectivereflection wavelengths of the at least two layers of the reflectionpolarizer (a) are superimposed on each other in the wavelength range of550 nm±10 nm.
 3. The viewing angle magnification liquid crystal displayaccording to claim 1, wherein the retardation layer (b1) is of acholesteric liquid crystal phase, having a selective reflectionwavelength band in a region outside the visible light region, and fixedin a planar alignment state.
 4. The viewing angle magnification liquidcrystal display according to claim 1, wherein the retardation layer (b1)is of a rod-like liquid crystal fixed in a homeotropic alignment state.5. The viewing angle magnification liquid crystal display according toclaim 1, wherein the retardation layer (b1) is of a discotic liquidcrystal fixed in an alignment state of a nematic phase or a columnarphase.
 6. The viewing angle magnification liquid crystal displayaccording to claim 1, wherein the retardation layer (b1) is a biaxiallyaligned polymer film.
 7. The viewing angle magnification liquid crystaldisplay according to claim 1, wherein the retardation layer (b1) is ofan inorganic layered compound with a negative uniaxiality fixed in analignment state so that the normal direction of a surface of thecompound is an optical axis.
 8. The viewing angle magnification liquidcrystal display according to claim 1, wherein the circular polarizationtype reflection polarizer (a1) comprises a cholesteric liquid crystal.9. The viewing angle magnification liquid crystal display according toclaim 1, wherein a λ/4 plate is disposed on the viewer side of thecircular polarization type reflection polarizer (a1), and an axisdirection of a linearly polarized light obtained by transmission and atransmission axis direction of a polarizing plate on the lower surfaceside of the liquid crystal display are disposed in alignment with eachother.
 10. The viewing angle magnification liquid crystal displayaccording to claim 1, wherein the viewing angle magnifying layer is adiffusion plate having substantially neither backscattering norpolarization cancellation.
 11. The viewing angle magnification liquidcrystal display according to claim 1, wherein all layers are laminatedusing a transparent adhesive agent or pressure-sensitive adhesive agent.12. A viewing angle magnification liciuid crystal display comprising atleast: a backlight system containing a polarization element (A) whereinsaid polarization element (A) comprises a retardation layer (b) and areflection polarizer (a), wherein said reflection polarizer (a)comprises at least two layers and said retardation layer (b) is disposedbetween said at least two layers, and said reflection polarizer (a) hasrespective selective reflection wavelength bands of polarized lightsuperimposed on each other to conduct collimation for a diffusion lightsource; a liquid crystal cell transmitting collimated lights; polarizingplates disposed on both sides of the liquid crystal cell; and a viewingangle magnifying layer disposed on the viewer side of the liquid crystalcell to diffuse transmitted light, wherein the reflection polarizer (a)is a linear polarization type reflection polarizer (a2) transmitting oneof linearly polarized lights perpendicular to each other, butselectively reflecting the other thereof, the retardation layer (b)comprises a layer (b1) having a front retardation of almost zero and aretardation of λ/4 or more relative to incident light incoming at adirection inclined from the normal direction by 30° or more, layers (b2)each having a front retardation of about λ/4 disposed on both sides ofthe layer (b1), one of the layers (b2) being disposed between theretardation layer (b1) and a corresponding linear polarization typereflection polarizer (a2) and the other of the layers (b2) beingdisposed between the retardation layer (b1) and another linearpolarization type reflection polarizer (a2), the layer (b2) on theincidence side is arranged at an angle of 45°±5° or an angle of −45°±5°relative to the polarization axis of the linear polarization typereflection polarizer (a2) on the incidence side, the layer (b2) on theemission side is arranged at an angle of −45°±5° or an angle of 45°±5°relative to the polarization axis of the linear polarization typereflection polarizer (a2) on the emission side, and the layer (b2) onthe incidence side and the layer (b2) on the emission side are arrangedat an arbitrary angle formed between the slow axis of the layer (b2) onthe incidence side and the slow axis of the layer (b2) on the emissionside.
 13. The viewing angle magnification liquid crystal displayaccording to claim 12, wherein the linear polarization type reflectionpolarizer (a2) is a stretched resin laminate with multiple layerscomprising resin materials having respective different refractiveindexes and retardation.
 14. The viewing angle magnification liquidcrystal display according to claim 12, wherein an axis direction of alinearly polarized light obtained by transmission of the linearpolarization type reflection polarizer (a2) and a transmission axisdirection of a polarizing plate on the lower surface side of the liquidcrystal display are disposed in alignment with each other.
 15. Theviewing angle magnification liquid crystal display according to claim12, wherein the selective reflection wavelengths of the at least twolayers of the reflection polarizer (a) are superimposed on each other inthe wavelength range of 550 nm±10 nm.
 16. The viewing anglemagnification liquid crystal display according to claim 12, wherein theviewing angle magnifying layer is a diffusion plate having substantiallyneither backscattering nor polarization cancellation.
 17. The viewingangle magnification liquid crystal display according to claim 12,wherein all layers are laminated using a transparent adhesive agent orpressure-sensitive adhesive agent.
 18. A viewing angle magnificationliquid crystal display comprising at least: a backlight systemcontaining a polarization element (A) wherein said polarization element(A) comprises a retardation layer (b) and a reflection polarizer (a),wherein said reflection polarizer (a) comprises at least two layers andsaid retardation layer (b) is disposed between said at least two layers,and said reflection polarizer (a) has respective selective reflectionwavelength bands of polarized light superimposed on each other toconduct collimation for a diffusion light source; a liquid crystal celltransmitting collimated lights; polarizing plates disposed on both sidesof the liquid crystal cell; and a viewing angle magnifying layerdisposed on the viewer side of the liquid crystal cell to diffusetransmitted light, wherein the reflection polarizer (a) is a linearpolarization type reflection polarizer (a2) transmitting one of linearlypolarized lights perpendicular to each other, but selectively reflectingthe other thereof, the retardation layer (b) comprises two biaxialretardation layers (b3) each having a front retardation of about λ/4 andan Nz factor of 2 or more, the slow axis direction of the layer (b3) onthe incidence side is arranged at an angle of 45°±5° or an angle of−45°±5° relative to the polarization axis of the linear polarizationtype reflection polarizer (a2) on the incidence side, the slow axisdirection of the layer (b3) on the emission side is arranged at an angleof −45°±5° or an angle of 45°±5° relative to the polarization axis ofthe linear polarization type reflection polarizer (a2) on the emissionside, and the layer (b3) on the incidence side and the layer (b3) on theemission side are arranged at an arbitrary angle formed between the slowaxis of the layer (b3) on the incidence side and the slow axis of thelayer (b3) on the emission side.
 19. The viewing angle magnificationliquid crystal display according to claim 18, wherein the selectivereflection wavelengths of the at least two layers of the reflectionpolarizer (a) are superimposed on each other in the wavelength range of550 nm±10 nm.
 20. The viewing angle magnification liquid crystaldisplace according to claim 18 wherein the linear polarization typereflection polarizer (a2) is a stretched resin laminate with multiplelayers comprising resin materials having respective different refractiveindexes and retardation.
 21. The viewing angle magnification liquidcrystal display according to claim 18, wherein an axis direction of alinearly polarized light obtained by transmission of the linearpolarization type reflection polarizer (a2) and a transmission axisdirection of a polarizing plate on the lower surface side of the liquidcrystal display are disposed in alignment with each other.
 22. Theviewing angle magnification liquid crystal display according to claim18, wherein the viewing angle magnifying layer is a diffusion platehaving substantially neither backscattering nor polarizationcancellation.
 23. The viewing angle magnification liquid crystal displayaccording to claim 18, wherein all layers are laminated using atransparent adhesive agent or pressure-sensitive adhesive agent.
 24. Aviewing angle magnification liquid crystal display comprising at least:a backlight system containing a polarization element (A) wherein saidpolarization element (A) comprises a retardation layer (b) and areflection polarizer (a), wherein said reflection polarizer (a)comprises at least two layers and said retardation layer (b) is disposedbetween said at least two layers, and said reflection polarizer (a) hasrespective selective reflection wavelength bands of polarized lightsuperimposed on each other to conduct collimation for a diffusion lightsource; a liquid crystal cell transmitting collimated lights; polarizingplates disposed on both sides of the liquid crystal cell; and a viewingangle magnifying layer disposed on the viewer side of the liquid crystalcell to diffuse transmitted light, wherein the reflection polarizer (a)is a linear polarization type reflection polarizers (a2) transmittingone of linearly polarized lights perpendicular to each other, butselectively reflecting the other thereof, the retardation layer (b)comprises one biaxial retardation layer (b4) having a front retardationof about λ/2 and an Nz factor of 1.5 or more, the slow axis direction ofthe retardation layer (b4) on the incidence side is arranged at an anangle of 45°±5° or an angle of −45°±5° relative to the polarization axisof the linear polarization type reflection polarizer (a2) on theincidence side, the slow axis direction of the retardation layer (b4) onthe emission side is arranged at an angle of −45°±5° or an angle of45°±5° relative to the polarization axis of the linear polarization typereflection polarizer (a2) on the emission side, and the polarizationaxes of the two linear polarization type reflection polarizers (a2) arealmost perpendicular to each other.
 25. The viewing angle magnificationliquid crystal display according to claim 24, wherein the selectivereflection wavelengths of the at least two layers of the reflectionpolarizer (a) are superimposed on each other in the wavelength range of550 nm±10 nm.
 26. The viewing angle magnification liquid crystal displayaccording to claim 24, wherein the linear polarization type reflectionpolarizer (a2) is a stretched resin laminate with multiple layerscomprising resin materials having respective different refractiveindexes and retardation.
 27. The viewing angle magnification liquidcrystal display according to claim 24, wherein an axis direction of alinearly polarized light obtained by transmission of the linearpolarization type reflection polarizer (a2) and a transmission axisdirection of a polarizing plate on the lower surface side of the liquidcrystal display are disposed in alignment with each other.
 28. Theviewing angle magnification liquid crystal display according to claim24, wherein the viewing angle magnifing layer is a diffusion platehaving substantially neither backscattering nor polarizationcancellation.
 29. The viewing angle magnification liquid crystal displayaccording to claim 24, wherein all layers are laminated using atransparent adhesive agent or pressure-sensitive adhesive agent.